[Jeff Burger]

fuchs?
targa or coupe ?
4 or 5 speed 901 or 915?
S brakes ?
pictures?

these are critical questions in setting value - that said lets summarize:

1. it needs interior work - headliner and dash
2. rust and paint work
3. mechanical work
4. a non matching (internals unknown) smaller discplacement then stock 2.0 motor that "needs a tune up"

That said with the limited information and the amount of work it is going to take to get it back to a real nice car , I think your offer would have to be under $10 k to be " fair" to you.
( admitedly sport seats are minimum plus of $2500)

Good luck jeff