Just an update, in case it means anything to anybody later: JVC Accessory Store (jvcpartsstore.com) has still not yet fulfilled my order. I received confirmation, but nothing since. Still keeping my fingers that the parts still exist, but not counting on it.
The lamp in question, though, started working again, intermittently. I removed both lamps (they twist off the back of the LCD/Operation P.C. Board) and applied some DeoxIT D100L (the viscous, red stuff) to the contact points. Now, both lamps are working consistently.
I replaced the RW/FF belts and carefully cleaned off all of the residual belt goo from the mechanism. The speed is dead on and constant with the original capstan belts (I thoroughly cleaned them and the pulleys then used a test tape to confirm speed), but the auto stop was clicking, intermittently, during playback (on whatever deck wasn't in play mode). I regreased the autostop gears on both sides and haven't heard the click since (keeping fingers crossed on it'll stay quiet).
View attachment 62044