I could be wrong but, my experience with ac systems went from 0 to more than the guys at my local MB dealer in about 3 months.
The compressor in your car is a General Motors product located on the cars bottom left engine sections. If you talk to any parts store they will tell you that it is cheaper to buy a rebuilt than fix it yourself. This may be true. I have never seen rebuild kits for cars as new as the 80's. Hopefully the other guys have a better answer for you.

Good Luck!!!!