The particulars of changing a tire vary with the airplane. Some require a wheel packing, some don't. Most require a wheel inspection, and many require stripping the wheel and performing a magnaflux or other inspection. Generally at a minimum a thorough inspection with a 10X magnification lens is necessary.
Prior to removing the wheel assembly, a thorough inspection should be made of the wheel, the tire, it's wear (important clues about the tire, the condition of the wheel, the axle, and the gear which may have a bearing on future maintenance and your current project). Look for uneven wearing on one side, shoulder wear, etc. Look the brake assembly over very carefully.
When the wheel is removed from the aircraft, the bearings come off with it. Additionaly for the mainmounts on most light airpalnes, disassembly of the brake is also required to remove the wheel. The bearings must be kept in their respective places, and should be thoroughly cleaned, air dried, inspected, and repacked. The races must inspected and lubricated. Generally the bearing packings are different on each side and must be kept separate. The axle area and brake assembly should also be inspectd and cleaned at the same time. The brake pucks often tend to extend, rebleeding the brakes is usually appropriate. You should inspect the brake pads for cracking, leakage around the pucks, etc. Check the brake lines for conditiona and security.
When the wheel is removed, it should be deflated. Deflating a tire assembly has been known to cause injury just as inflation has; mechanics have been injured or killed going both ways (usually overinflation, but during disassembly, too. One sure mistake, and I've seen several make it, is attempting to undo the wheel bolts prior to tire deflation. When the assembly is deflated, the bead on the tire must first be broken before undoing the wheel bolts. The bolts are then removed. If this is done carelessly, the mating flange can be damaged as it chatters. The wheel halves must be kept oriented to ensure that the same bolts and holes are used; each half should be marked to keep it's relative position to the other for reasons of both stress and balance.
The wheel halves should be thoroughly washed in solvent, then usually in hot water and dried. Any rubber deposits should be removed. Care must be taken in cleaning the wheel assembly to avoid damaging any metal treatment or coating, unless it's required to be removed. A thorough inspection at a minimum should be made using a 10X power magnifying glass for distortions, cracks, excess wear, dents, etc, with particular care being made with rim areas, the bead areas, and the mating surfaces at the inner flange. Some wheel assemblies have life limits or require specialized dye penetrant or other inspections, and as airplanes get larger (many twins, on up), the requirement is often nearly universal.
In all cases the bolts should also be equally inspected, and in many cases the bolts must be subject to dye penetrant or other inspection means, as well. Pay close attention to the locking nuts to see that they still conform to standard, meet the minimum exposed thread, and are within specification with respect to finger tightness and condition before futher use.
Many wheel assemblies use an o-ring packing at the mating halves to seal them; this generally for tubless assemblies. A new packing must be used.
Properly done, the wheel assembly should be checked for balance prior to mounting the tire, and this is done by reassmbling it witout the tire, and putting it ona balancer to note the heavy spot. It is then again disassembled, the tire put in place, and reassembled. When assembled it must be torqued. This isn't a matter of simply tightening down the nuts. the bolt heads must be kept steady and only the nuts turned, and these must be turned in the proper order. A pattern is used, generally with a two-step torque process. This involves tightening all the nuts to a predetermined torque in specific cross-bolt pattern, then retightening them to their final torque. Failure to do this can result in wheel failure in operation, or simply under the load of inflation, and can crack the wheel assembly now or later. Absolutely ensure that washers areunder each bearing surface of the fasteners, particularly under any rotating surface (such as the nut, for example), lest you induce stress risers which can also cause part failure.
If you've installed a tube, ensure it isn't pinched by slightly inflating it with the needle valve removed, prior to tightening down the wheelhalves. You'll also have wanted to make sure you have placed the heavy point on the wheel (marked with paint from the factory) opposite to the heavy point on the wheel/tube assembly (typically, but not necessarily) opposite the valve stem, if there is one). With the tire in place, the entire assembly is then again placed on a spindle balancer and checked for balance. The wheel is rotated around inside the tire repeatedly until it's found to be closely balanced, then weights are applied (3 oz. max) to bring the wheel assembly fully into balance.
Ideally the process should then take place inside an inflation cage; mechanics have been maimed or killed with wheel assemblies that failed during inflation. Using nitrogen, the wheel assy should be inflated partially, using direct air through the stem and no stem valve, until the tire bead seats. It should then be deflated, and reinflated with the valve stem in place. Once inflated, it should be checked again for final balance, as this does sometimes change, and adjusted as necessary. A thorough inspection of the completed assembly with a soap or leak detection fluid used on the valve stem and tire bead areas should be performed. A notation should be made regarding the final pressure. The bearings are then repacked with the appropriate grease and reinstalled, and the wheel remounted on the axle, and the brake reinstalled on the wheel assembly. The brake usually requires proper safety wiring, and if the puck(s) are at all extended, then the brake assembly should also be bled. The axle nut should be reset in accordance with the maintenance manual, which is a several step process in most cases involving torquing, loosening, and retightening, with new bolts or a cotter pin installed. How you install the cotter pin makes more than a 50% difference in it's strength, and lest you think that's too much, I've seen improperly installed ones depart the aircraft.
You're not done. 24 hours observation is required with a leakdown check the next day to determine how much pressure has been lost (also in many cases to see if you've pinched the tube; you may not know right away), reinflating the tire to it's proper pressure, and of course, making the appropriate paperwork complete. That's one tire, and a simple one. This hasn't addressed the appropriate use of chocks and jacks, etc. Jacking one wing is generally not appropriate, and that depends very much on the airplane in question, too. I've see airplanes damaged from imprope jacking, and not just from dropping one; tipping the airplane or sideloading the gear, or attempting to jack while tied down or putting uneven twist or presure or tension on the airplane can do it, too.
Sure, you've probably been cranking them out in a half hour...but you've not been doing it properly, either.
What do I charge? Base rate 50.00 dollars an hour. However, there's nothing preventing you from doing the work yourself. You just need to make sure you've done it properly. Do you know how to do that? Does anything I just described sound foreign to you? Do you have the appropriate tools? Are your tools calibrated? Have you performed the work before (properly)? Are you using nitrogen? Do you have the manufacturer's current publication before you? Not just a copy of the mx manual, but a current copy? Do you have all the appropriate data? Not just the airframe manufacturer's manual,but the wheel manufacturer's manual, the brake manufacturers manual, any relevant supplemental type certificates, service bulletins, and airworthiness directives, and are you able to comply with all of them?
These are minimum performance standards for any mechanic (engineer) doing the work; you're expected to abide by no less.