More tinkering today. Replaced a/c compressor. First time in a Merc so it took a lot longer than it should have. I think I have a vacuum pump somewhere but may have to get one from Harbor. Also need gages. Next up is to replace receiver drier and then pull a vacuum. While the plastic under trays were off, replaced a missing threaded insert and screw. Also replaced two other screws with OEM. Trays are firmly attached now. Did a shade tree alignment to try to get steering wheel straight when going straight. Yes, yes, not supposed to do that but this bugged me enough to consider a shop alignment. Also checked and re-attached transmission ground. While everything was apart, looked for an oil leak at the front of the engine. Suspect it is combination of oil filter housing and old compressor. Spent a fair amount of time cleaning off oil muck.