I think that swapping a clutch would be VERY hard whilst the compressor is on the car. If you think you can, then fine, but I believe the clutch is pressed onto the compressor shaft and has a key. I could be wrong.
If you need to either take the compressor off the car or need to swap the compressor, take it to an A/C shop and buck up: depending on the year of your vehicle, It's not legal to open up the lines and vent refrigerant, and you can't test the system without a vacuum and proper gauge to make sure it will hold pressure after reinstallation.
91-93or4 systems came with R-12, which is not only not produced anymore, but is VERY expensive, so it is always reclaimed when draining a system. This takes specialized equipment that an A/C shop has. This is due to the fact that it is now illegal to produce in most countries because if it's status as a very potent
greenhouse gas. it can still be purchased, but only with a special permit. R-134A is a fraction of the cost and can be obtained over the counter.
In 94, the switch was made to R-134a. R-12 and R134a are not compatible and will lead to system failure often resulting in compressor seizure at worst, system leakage at best. R-12 and R134a systems use different seal types and different fill and drain valves to avoid using the wrong stuff. You cannot use R-134a in an R-12 system without fairly extensive conversion - to put in in truck terms, think of mixing Red and Green coolant and never checking it again... Except worse. Conversion involves evacuating the system, flushing (including compressor), changing all seals to a 134a compatible type, changing drier, evacuating again to test for leaks, then filling.
I learned this (for better or worse) working for a compressor remanufacturer in Dallas for 3 1/2 years.
