That was Trek's top of the line bike back then. The 770 was probably a little more expensive because of the Campy SR components, but the Superbe (super bee) Pro components were arguably better if not as prestigious. Personally, I don't think I would go more than $300 unless the paint was in pristine condition.
If you plan on replacing everything with modern components, you can probably sell the Suntour stuff on Ebay for some pretty good change. But I would keep it as is for a while. You might find you like it.
The rear should be easily capable of being spread to 130mm.
Here is the page from the Trek catalog courtesy of vintage-trek.com.
Note that the stock wheels were for tubulars.