Is this still pilot allowable maintenance ???
To answer the question properly:
Aircraft tyres use a Schrader valve the same as a car. So car pressure gauges and pump fittings work.
Nitrogen is a technically better gas than air for both cars & aircraft. It doesn't permeate the rubber (ie leak) as easily as air and its heat dissipation is better. However, like cars, most GA aircraft just use air and only high performance cars / aircraft bother with it.
You'll need to check the Flight Manual for tyre pressures, but they are typically in the car domain, ie most are 35 - 50 psi. Cubs & other light aircraft are maybe 12 - 15 psi. The rule of thumb is that tyre beads become insecure on the rim below about 12 psi.
Correct pressure will enhance both wear life and braking performance.
Some aircraft require a hub cap to be removed to gain access to the valve.
The $10 gauges that you buy from the car accessory shops are not too bad in terms of accuracy. Just buy one of those. Don't trust an airline gauge (ie the service station type incorporated in the hose fitting) these are notoriously inaccurate, even before they get driven on or thrown across the workshop / hangar.
Check the tyre pressures, you may be disturbed by how low they are - not many other people check them. And do your car while you are at it.