If it were me, here's what I would do with a new-to-me-rig in which the AC doesn't work. In fact, I was in the exact same boat when I bought my '93.
Just because the guy you got it from says the compressor is bad doesn't make it so. If it is low on refrigerant (leak or just low), it will not click on. I would test the compressor before blindly replacing it.
For me, even though it came with R12, I'd recharge with R134a. It is cheap and easy to find. I used R134a in my '93 and have been happy with it. Seems to get very cold but I don't live in AZ either.
Replace all the O-rings. Again, cheap and easy. I use Nylog blue on all fittings / O-rings (as suggested by someone here). Seems like good stuff.
I'd replace the expansion valve. Again, cheap and now is the time to do it since you are opening up the system. Also gives you a chance to clean the evap unit which is undoubtedly in desperate need of cleaning.
And of course the dryer gets replaced.
All the tools you'll need can be "rented" (i.e. borrowed for free) from the auto parts store. You can get the AC manifold and a vacuum pump. Also, the parts are all available on Rockauto for a reasonable price.
Good luck. There are lots of threads here on AC, so do some research here. I have repaired both my '93 and '95 and they both work great. And I had never worked on AC before doing the '93.