take the belt off to see if it stalls after you start it.
if the clutch on the compressor is shot, just buy a new compressor. changing its not worth it in the long run.
if you plan on doing this yourself, find a shop to vac out the a/c system for you, go home swap your compressor and its best to swap the orifice tube as well at the same time. take it back to the shop and re use your old R what ever it is that the shop has on hold for you. of course they will charge you to empty and refill your system but you know it was done right.
