whiterabbit.. I was playing around on ps last night, and if you look in the color change tutorial, it tells you how to do it.. While it's not as deep/rich of a black as omicron got, if you mess with the color curves after selecting the car body and deselecting the windows, etc, you can get a pretty good black. And use the magnetic lasso tool to select the car body... I am soooo in love with that button right now.
I don't think it's possible to do believable black in paintshop.. I have yet to find it anyways.