Ok, Hitcher, I was still somewhat defending you in my previous post, but from what I read now it's obvious. Stay away from a/c please. You cannot check tires visually like your bike tire. 50 PSI decrease in a tire can be enough to replace both wheels on an axle, but this amount will not bulge the wheels as you might think. A kick with your foot will certainly not be legal as inspection.
And yes we drink coffee and pour some oil in from time to time, things a monkey can do, but to be in charge of engine changes, flight control replacements and riggings, major avionics rewiring etc is another thing. Of course these things you'll not notice as a guard as you only see line maintenance.
Many of us did study 6-8 years to get all the licenses and still have to learn, something a car mechanic or you will not have done. All security guards I know have followed a 3 days course in an interim bureau. What's even wrong with being a car mechanic?
I really hope you give up your plan to become an engineer, you'll have diminished your chances to find work anyway, aviation is a small world.