I've got the Sport Designs on my 996 and they were also looking a little tired. They had a lot of curb rash and the centers were kinda nicked up. I also wanted to do a color change. Without dismounting the tires, I separated the centers from the barrels. On the barrels, I was able to use a file & sandpaper to knock down & smooth out some pretty bad curb rash. I used a paint stripper and steel wool to remove all of the painted finish, then I polished to a shine (lots of elbow grease). So far, I've just used polish to keep the rims clean, and it works OK. I've heard of a product called Sharkhide that I'm going to try.
For the centers, I took them to a local powdercoating place. They charged me $320 to strip and coat all four centers, and they turned out beautiful. money well spent. Separating the centers from the barrels was just a matter of getting the correct bit and pulling each bolt. Assembly was just as easy, and I applied a little blue loctite for insurance.
