Your best bet is to learn from the ground up. Inevitably if you own a pin your going to have to work on it. Like you I was not going to spend 6000 on a unit. To me that is just too much. I grew up in the 70's and EM's were the rage so I found one for 650 and then another for 700. Then the kids and the grand kids wanted ramps and things so I got lucky and bought a Monte Carlo....it was a great game and a hit with all the family spent 1100 for it...not a bad deal. Flipped the first two machines and bought two more system 80's. yes i have had to work on them all but I now have 3 games and only 3000 invested and they all play like they were when they were new and now I know everything I need to know when it comes to fixing them.
If you don't know how to fix them you're going to shell out big bucks every time they break or you will end up like a lot of people who just have broken machines siting in their house collecting dust and taking up space and eventually selling them for far less then they are worth