If the clutch disengages properly then the compressor should not be running. Most likely the clutch itself is bad instead of the compressor.
If it is working fine, and the noise is only when it is disengaged you should only need to change the clutch on the compressor not the entire compressor. If there is room to pull the clutch off on the truck, then there is no need to evacuate the refrigerant.
Yes
There may be some drag on the AC clutch when it is disengaged as the clutch 'free-wheels' during this time. When you engage the AC ,the clutch 'locks up' and the noise disappears. If the noise gets worse you may need to replace the clutch, if it stays the same and it not very loud, I would not replace it.
If the AC pulley is locking up when the ac compressor clutch engages, it's not a clutch problem, it's a compressor problem. But yes, the AC clutch can usually be replaced separately. The problem is, if the clutch is worn out the compressor is probably worn out as well. It usually isn't that much more to replace the whole thing.
You cannot change the compressor bearing, however, you can change the clutch bearing. Which one is bad? Is there a noise when the clutch is engaged, or not engaged?
Could be the clutch is gone. If that is the problem, you can have just the clutch changed, but don't wait too long. If it is the bearing, then have to change the compressor. When it is running, you will see the clutch wobble. The clutch can be changed with the compressor on the car. There is room.
No, oil will ruin the clutch. Noise that sound like you need oil means a bearing or the compressor has failed.
the clutch on your A/C compressor needs to be replaced.
bearing is shot
Yes, if the compressor's bearings are bad, usually accompanied by a roaring or squealing noise coming from the compressor's pulley.
The clutch assemble is shot...
Check the ac compressor and clutch to see where the noise is coming from. Also check the compressor drive belt for wear.