Great game, and really not a bad price. You say you're not sure how to work with electrical, but this isn't necessarily a bad way to learn. There are guides out there (at least general, not sure about the specific Gottlieb guides). Keep in mind, you'll need to get a Digital Multi Meter and a temp controlled soldering iron. It's up to you if you want to add that to the cost of the machines, or chalk it up as a long term investment (I'd say the latter if you plan to continue doing your own work).
These things are supposed to be pretty solid once all of the mods are completed. The price isn't bad, but it really depends on the cosmetic condition. Take a look at the board around the battery holder, it it looks like it has a lot of bubbling around that area, then it could be a lot of work.