Follow-up. The adapter part came in (turns out it's made by PIE). Installed the part. Clean, plug-in installation, works as advertised. It has two RCA jacks coming out of it, which I attached via some soldering and some adapters to an 1/8" stereo mini jack mounted cleanly in the storage pocket below the stereo. Plugged a portable MP3 player into it, sounded great, albeit at a slightly lower relative volume than the CD player. Now, I have only to wait for the Pearl to come out.

Regarding the air conditioner: I can't see that I did anything wrong. All wiring is correct, all buttons and knobs work and do what they're supposed to do. Everything about the air conditioner appears to work except the "cold" part. For instance, when I press the AC button, the engine lugs and I can hear the compressor under the hood engage and begin working, so I know she didn't lose a belt. Afraid to look under the hood now, fearing I'll see a hose that popped off.