I'm replacing the AC compressor of my 87 300D because the compressor leaks refrigerant. The compressor still works, a trusted shop don't think it sent shrapnel through the system. My plan thus is to replace the compressor and have the system recharged with R-12.

There's a list of items I can change (expansion valve, drier, etc.) but I'd like to know what I should change.

Questions:

1) A shop I trust says there's no need to replace the drier if the system is clean and hasn't been exposed to moisture. What are the pros and cons other than cost?

2) Ditto the expansion valve?

3) Should I replace other system seals, at least the ones in the engine bay?

4) Which are better - green o-rings or black o-rings?

5) There is grime around the low pressure Schrader valve. I clean the area and it's grimy again by the next oil change. Should I replace the Schrader valve?

Thanks,
Sixto
87 300D