A/C Compressor Issue

I'm trying to deduce what is going on with my sisters car. it's a '96 Tercel. The A/C hasn't worked since she bought the car some years ago. She tells me it started running really bad and smoking. Upon investigation her A/C Compressor is not spinning and the belt heats up like mad in only a matter of seconds and smokes. I asked her what happend to make it do this all of the sudden. She said she didn't know but that someone else drove her car and they kept turning the A/C on even though they knew it didn't work. So here are my questions:
1) Did he cause the clutch to freeze by hitting the damn button?
2) How do I get her back on the road? (she cannot afford to fix the A/C system.)
3) Can I replace the compressor with a used one that doesn't work but isn't locked up?
4) Is it possible to just replace the compressor clutch?
5) EXACTLY what is involved here? - I am mechanically inclined and can do most stuff but I work on old E21 BMW's (77-83). Is this a bitch to do?
There's not a lot of room to work on these things. Again, I have NO experience with A/C stuff. Any special tools to remove the compressor IF that's what needs to be done?

Sorry so long a thread but as I said I know nothing about these cars. I'm just trying to get her car back on the road so she can get to work.

Thanks folks!