Is this replacable by itself or does the whole compressor need to be replaced?

I got a quote for over $1K for just the compressor which seems very high.

 

The FSM shows how to replace the clutch assembly and it looks fairly easy. I know that's never the case but... If you end up deciding to buy another compressor try car-parts.com to find a used one near you. Most people I know with compresssor problems replace the compressor with a junk yard model and do all of the installation themselves except for evacuating and recharging the system.

 

scan the local junk yards, nissan dealer do not sale them they will sell you the whole compressor only