To go from a darker color to a lighter color will I really have to re-prime my car again, I have been thinking about going from Black Cherry to Performance White.
At the very least you should seal the color your painting over to prevent lifting/bleeding of the underlying color(you can tint the sealer). Your going to use alot of paint if you dont tint the sealer... BUT...If the existing color has any defects, repair em or they will come back to bite you.
Runs...Orange peel...Nicks...scratches...flakeing/bubbled up paint etc... Allways remember...Paint does not fill dents...scratches...or holes. As long as the paint is solid, you can sand, repair, fill,prime and seal right over it. You want to look for any areas where the paints adhesion has been compromised and repair those defects. Then seal and paint. Also... Your paint finish will only look as good as the foundation you put it over.