On the vintage trek site, there is a page showing models, colors, and years. You can use that to track down the year and then google the catalog to figure out the specs.

https://www.vintage-trek.com/images/...rek/90Trek.pdf

Edit: I think $150 is on the high side but anywhere between $75-$125 is fine for this bike. You could offer $100 and settle on splitting the difference. $125 is not a crazy price for this bike and the multi-tracks make fine all around utility bikes.