Dude... for all the crap we give you, you've got a car you like. For all appearances, it's got a straight chassis (through whatever miracle - and that's not meant to be a slam, just stating fact). It looks like you want it to look, and it sounds like it drives how you want it to drive.
It doesn't matter a whit if the car is worth something to someone else as long as it's worth something to you. My car needs a trip to the body shop - if I were interested in selling it - because it has cosmetic damage that reduces its value to someone else - and probably reduces it more than the cost of fixing it. But... I can live with the boo-boos.
If there's stuff you want to do to your car, don't think of how it affects resale value - think of how it affects value to you. If you can crunch the numbers and figure out the $$$ payback to your pleasure, it probably makes sense.