I refurbish and sell a lot of older bikes. My pricing scheme is pretty simple...I take the MSRP and cut it in half. Then I adjust up or down depending on age, condition, etc. That figure sounds about right for the bike you're talking about.
Provided the thing fits you, you'll want to check and make sure everything works. Shifters, brakes, etc. Make sure there are no obvious dents, dings, or cracks in the frame, and that it goes straight...
Wheels should be true and the tires should be at least in decent shape.
It's very difficult to check things like wheel bearings and such without pulling the wheels off. A wheel that spins easily on the bike might feel like someone poured sand in the bearings when you move the axle by hand.
See if the shop is willing to stand by the bike for at least some period of time.