There are several internet sources for AC compressors (and other componnents) - both new and rebuilt - that are a lot cheaper than local. It's not difficult to replace the unit. However, one thing you MUST do is evacuate the system using a vacuum pump before re-charging using good gauges. Very few tool places rent these pumps anymore but you can buy one for less than $100 that works off an air compressor (if you have one). If your system is contaminated from a burned compressor, that's another problem entirely.
Lots of good AC links out there with lots of info. I did a conversion from R-12 to R-134a on my old 5.0 and it was quite successful. However, I replaced the compressor, condensor, both lines and all seals.
Good luck.
