2000 trx400ex

Hello all, been lurking here for a bit. Nice forum, good knowledge.

I am looking at a 200 TRX400EX, here are the issues that I know about.

No rear brake caliper, found several on ebay for less than $100.
Needs a clutch, found them between $50-150 from varies places.

What I need to know, how do I check the transmission and gears if the clutch is toasted?

He say’s the motor runs and will fire right up, ok, good. But how to check the other major areas of the quad if the clutch is not working?

Thanks in advance