I have a 2004 TT 3.2L that (according to my mechanic) is starting to leak oil from the A/C compressor. After a bit of research, it seems as though the seals are not replaceable. Without adequate lubricating oil, I understand that heat & friction can cause metal bits to clog the system resulting in a more expensive repair. So it seems prudent to replace the compressor.
This gives rise to a couple of questions:
1. Am I correct in assuming that the A/C compressor needs to be replaced?
2. Is there a significant difference in both quality & price between an Audi factory compressor & an aftermarket unit?

Thank you so much for your input.