I've never done it, but reasearched it once when I thought the clutch electromagnet was burnt out on my dauighter's car. That ended up being a broken ground wire.

There is a little nut on the front of the comrpessor. That's there partly for decoration, partly just as a secondary failsafe. Because the springloaded clutch plate that drives the compressor (when pulled by the magnet back against the pulley) is really just pressed onto the shaft, using an intference fit (i.e. jammed on really hard). This requires a special tool to pull it off (you'll almost certainly destroy the clutch plate trying to take it off without the special tool), and a different special tool to reinstall it (where you need to pay attention to the air gap between the clutch plate and pulley).

Once that is pulled off the compressor shaft - then there's judt a circlip that holds the freewheeling pulley on.
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'63 PV544 rat rod, '93 Classic #1141 245 (now w/16V turbo)