If the car is really in nice shape, at 100K, it's probably a fair price. Look at the brake fluid, if it's really dark or black, the flush hasn't been done. if this for example was neglected you'd be left wondering if anything else has been skipped on. For the price I would expect the tires will be good for over a year as well as the brake pads. Find out if the climate control filter was done, including the charcoal filter which is about $200 and is supposed to be done every 45,000 miles. Watch for any leaks from the side seals on the rear differential.
And of course check out the body for dings, wheels for scraping on the edges, things like that. Like I say, if it's a straight body and the maintenance has been kept up "to the letter" it's probably a fair price. Check Kelly Blue Book (KBB.com) to recheck the price for your area.