My A/C system blows ice cold, but last summer the compressor started making a squealing sound whenever I was in gear, and at a stop. So I replaced the clutch and bearing assembly. The clutch was totally smoked. That helped for about 2 days, then the sound came back. So this summer i pulled my clutch apart, and pulled one spacer out, thinking maybe it was gapped too much. Got it down to like .0015, clutch still looked ok. That didn't help. Every time the compressor cycles on, it sounds pretty bad, so I'm thinking that it is starting to seize up on the inside. Car has 200,000 miles on original compressor, 09 Mariner. So am I looking at replacing the whole AC system because of contamination?

 

Appears you are on top of the situation.
Total replacement may or may not be required depending on how much got loose in the system and if some parts can be saved by flushing out the system.
The more it is allowed to go downhill the more expensive it will get.