The most important thing is the playfield. Try to get a nice one with as little wear as possible.
Check the MPU. The batteries can leak and damage the board. I just replaced mine with a $300 aftermarket board since the original was badly damaged. It is probably repairable, and I will get around to it one of these days, but I wanted a better one since Pinbot is a keeper game for me.
Probably make sure the ramp is in good shape; I am not sure if those have been reproed. The playfield, mini playfield, and vortex plastic have all been reproed, but the playfield is expensive. Not sure how hard it is to find a backglass, so you probably want to make sure that is in good shape.
I can't think of anything else that is too hard to fix, so I probably wouldn't worry too much about the other stuff.
The game lists for (I think) $950. To me, that should mean that a 7/10 should cost about $600 or so, but it is getting to the point that that doesn't seem to be the case anymore. I have seen a few in that kind of condition go for around $900. Nicer ones seem to go for $1200 or so. I have about $1000 into mine, and I had to spend a few days to get it running and sorta shopped. I am going to shop it properly hopefully next year, but there are too many other projects ahead of it.
If it is a game you like, I would definitely pick it up. It took me about 6 months of serious searching to find one, and I found a project that I had to travel 400 miles round trip to get. It turned out great for me, even though I swore off projects a while ago.
