if done correctly, you can do some awesome paint work that'll hold true for years. im plenty of people on here have painted some parts of theirs. go look in the paint/appearance/detailing section of the forums and check some of them out.
overlays aren't really cheap but alot of them look like it so be careful. there are nice ones out there but some just look tacky.
hydrodipping or wrapping your interior parts would be the best way to go about it, imo. the materials really dont cost that much for what your getting and it looks incredible. 3M has some quality wrap if your skilled enough to do it. i failed at it so im going to use hydrodipping. i figured it to be approx $200 give or take to dip the interior.