I just did this repair on my '96 960 last week. I bought a used compressor ($75) from Strandberg's Volvo Salvage in Wisconsin, removed the clutch, pulley/bearing, and coil from the old compressor and installed the used ones from the replacement compressor. I didn't have to open the refrigerant system. I ended up removing the radiator for more room, used 3 bolts (1/4 x 20) in the holes on the clutch to remove it from the compressor shaft, spring clip pliers to remove the clip holding the bearing/pulley, wedge this off with screwdrivers, remove another spring clip holding the coil on. I found great instructions in the FAQ and on the Sanden website.
Marlin