1994 Quantum Pro won't have any non-standard bits other than the steerer tube size. If you're sure the stem is a good fit for you it'll make a great bike. Swapping stems would get complicated though, same with the fork and headset.

It's worth as much as the seller can get for it... but I'd expect it to go for ~$300. A 1998 Quantum Pro frame retailed for $1600.

History of Klein Road Bikes on my Blog: LINK