yep, I agree with the quotes of $3K being the top value that you want to pay for it. most of the items sound like they should be easily fixable.
the lamp + flasher test shutting down the entire machine is the one that I would be most concerned with, but could be an old fuse on it's way out, idc connectors needing to be re-seated or a new connector.
another thing to check for is any dark or black marks on any of the idc connectors. where ever you have "burn" marks, current is being impeded. those connectors and the wiring should be looked at.
additionally, if the owner will let you, have him disconnect and remove the dmd display board and inspect it to see just how crispy it is on the back side (high voltage section, which is the lower, center section). those 3 cement resistors get awfully hot and can do a lot of damage to the board in that area over time (especially games that were routed for a long period of time and left on 24/7 or most of the day)