Very rare for a Bally Star Trek to have a ''great condition'' playfield, I have not seen one original that was not worn in some way.
However, CPR has done a run of playfields, I bought one from them as I have two Star Treks. One of mine is a great player, the other is in pieces but just about all there)
Other area of concern with these is the backglass, especially at the bottom (they bubble or flake) I got lucky with my two, one is very nice and one is near perfect.
Check for battery acid damage on the cpu, very common. Fixable, but a pain in the ass. Alltek cpu is a better bet, or a good solid used one for half the $$
I'm guessing the capacitor could be anything from the sound board or the driver board. The sound boards are rare/hard to find but if it's present there are people here that work on them. More than likely he is talking about a driver board capacitor. Alltek makes all the boards (except sound board) for these pins.
If things check out okay, then the price seems reasonable to me.
Good luck, fun pin.