Most likely they are 235/65-17's that you could pick up a new one for $130. I would say if your selling it private party replace the tire buy if your going through a dealership a don't bother with it. Don't let them low ball you though, know what your car is worth before you go in.
If you are trading it in leave it as is. They twist it around no matter what the car has. If it has all 4 new tires they say "oh that doesn't add to the value", if it has 4 bald tires they say "oh that devalues the cars value so we have to give you less for the trade".