BMW Repair: 1997 BMW Z3 1.8 liter, kuni bmw, bmw z3

Question
I had my 1997 BMW Z3 painted & when I went to pick it up it wouldn't start. Had my mechanic come by and he changed the plugs & put in a new fuel pump. It turns over but won't start. Took it to the Kuni BMW dealer and they can't seem to figure it out. They want to pull the cover off & check the positioning of the valves to see if it's the timing or they think it might be the brain. I towed it back to my house until I can afford that but want to know which I should try first. My thought was the brain because everyone that check it said it wasn’t throwing codes even after they reloaded the software. They want to charge $450.00 to check the valves first. What should I do first and what is your recommendation on buying a used brain. What do I need to look for if buying used brain (is it ok if previously installed in a car) and if new where do I go to find one cheaper than the dealer?

Answer
First I find it hard to think a BMW computer to fail with what has been done.Do you have spark?You mentioned a fuel pump,what is the fuel pressure?If there hasn't been any mechanical tear downpreviously I would be looking into a ground that isn't connected or painted