Frogger, what is "not in good shape" about them?
They all get dull and kind of turn whitish.
If they have extra holes, some are factory, or cracked why not try your hand at plastic welding?
You can pick up a cheap plastic welder at HF with different welding rods for different types of plastic.
As for the whiting I don't really have an answer. Think some have used a little laquer thinner on a rag and wipped them down. Think others have tried heat guns to "melt" the top and bring the black back.
If you try either do it someplace it will not show up till you know it will work.
I think other have painted them but the thing is you have to prep the liners really really really good and use paint for plastic and hope it sticks.
On my truck I was not that worried about them to spend any time on them before I bolted them back in.
I am happy I did not as they got over spray on them when I painted the truck and I had the under side tapped off so that would not happen.
Dave ---