I had some pretty good success with using Mothers Brand "Back to Black". It supposedly restores faded plastic and bumpers etc. I don't think it brought them back to "new" but they look alot better after using it. The nicest part is it's cheap and easy...because if you paint the flares, I guarantee they are going to look "off" compared to your bumpers and trim that is plastic.

 

Look in the "Detail section", there is a current post you may want to also read.

 

Since my truck is white I was thinking of getting the paint code and painting them that same white, and possibly some of the other trim if it doesn't look right with the fenders white.

 

I have seen that done and I think that may end up looking better than if you did it in a glossy black (or even a matte black for that matter) Like someone said, It would be hard to match the rest of the black trim. The disco I saw it done on just painted the flares and i looked really nice, even with the rest of the plastic still black. Dupont makes some really high quality and tough auto paint so when you are in the market for paint check out their stuff. goo luck with whatever you wind up doing.