If you like the car, fix what's wrong with it and don't worry its
market value. Unless there's something catastrophic wrong with it, or
it's totally run-out (> 400,000 miles ?), fix it and enjoy it. You
have a years' experience with it. If you move to another car, you'll
have a whole new set of expensive unknowns to deal with.

Make sure your serious safety-related stuff is good ... brakes, tires,
steering. Then fix the stuff that will get worse/more expensive if
you don't fix it, and let the other stuff go for a while.