Man you've got to slow down, I can't understand 3/4 of your post.
Either way, $400 won't go far in rebuilding a head at a machine shop. Go as far as you can and know that you did as much as you could afford to do.
About a used head--who says it's any better than yours?
About cosmetics, dude, it seems to me you have a lot of much more dire things to spend your money on than making your car look clean, but hey, who am I to tell you how to budget yourself.