I need a replacement for the side marker lamp socket. Dealer only item or does someone perhaps have a GM part #? Off the one I have is 12020848 but it doesn't seem to match any online catalog.

If you are refering to the ones on the front bumper cover, visit any local auto recyclery/junkyard and they'll sell you one for cheap. I broke mine when I removed my front bumper cover on my 97 and got a replacement for $5. Also I don't have a part number, but I believe any from a 95-01 Lumina/Monte Carlo should fit.