I haven't tried the AC lately so I can't answer that one. The ring is a retaining ring is remember correctly.

I found the vacum line and stuck a screw in it for the time being to see if that worked. After that I made sure the hubs were locked and turned the drive shaft going to the front in. The axle on the drives side didn't turn, but the one on the passenger side turned. I tried it on the hill behind my house and it would climb it. I took the lock out apart to check things out and it looked fine.
Does the shift motor look like a small starter??