Follow-up: got the rebuilt LCM back from Jim and reinstalled, and all good. Air bag light went off, and air ride compressor stopped running once a minute. No clue how those are related, probably something with the maze of alarm wiring under the dash. All my interior lights and clock / radio / temp displays are brighter than they have ever been. Appreciate the quality work!

My underbody lights haven't worked for a while, and neither does my interior light come on when you unlock the car, which I think is also a pre-existing condition, and may also be related to my alarm dying. It's 16 years old after all. It used to chirp when I locked and unlocked the car, and hasn't done that for a few months. I think the underbody lighting and interior light coming on and the alarm are all related.

I'll figure it out, but now I don't have to worry about the lights at night at least. Nothing like driving down the freeway at 75 at night and having the lights randomly shut off!