That sucks vintagegamer. I just found your thread on KLOV (I think, just closed the window) Noticed you said the PCB was covered in black dust. If you're gonna be attempting to repair the pcb, best place to start is to clean it up with some compressed air, isopropyl alcohol, and q-tips. Go slowly, get everything clean, and examine the board while you're doing this, front and back. You're looking for any broken traces, any areas where it looks burnt, cold solder joints, roms that have popped partially out of socket, any legs on the chips that are bent up.
Are any of the chips on the board socketed? If so, take them out (gently) and clean the inside and outside of the legs with isopropyl or gently scrape them with a screwdriver for the tough dirt, then put them back in (again, gently, make sure the legs are all going in, and make sure the chip is in the socket the correct way).
I would test at that point, then go on to trace the coin up circuit on the board. From a brief look at the schematic in the owner's manual (
http://www.tamdb.net/index.php?page=ManualDetail&id=3047 ) it looks like the coin and test circuit is on page 26.
You may get lucky and find that it's something simple.