New tires and cleaning the fuel injection system and possibly new belts. How much would have the things you needed cost? I know cleaning the carbon build up in another brand of car costs about $480, tires looking at maybe $100 each plus mount and balance so that's about a grand right there and then I assume this car uses a serpantine belt but I forgot how much it costs to change those so maybe another $250 in parts and labor I dunno and a tune up, so you would have been looking at $17,000 negotiate with the dealer and another $1250.
I haven't ever negotiated a preowned car with a dealer but I'm sure there is a lot of room unless maybe it was a trade in. But if I was going to a dealer I would scoff the price and see if I could get it knocked down below book. That's just me, some people don't like to haggle and just pay up which is understandable too because the effort involved can be annoying.
For the tires, I would get them inspected and if tread doesn't fly off of them, they probably are fine. I changed the oil in a 1989 Hyundai that still had its original tires on it. It still worked. The rears on one of my cars are about 10 years old, they are fine and I'm not worried about it at all. Good Year told me that as long as I can inflate them to not worry about it. Exposure to the sun can shorten the lifespan of the tires.