You don't _need_ to repaint fork nor frame, you just want to. It's a bad bad bad idea to sand the clear and paint off carbon because the factory probably had materials scientists and engineers setting up the proper paint and you're probably neither if you're asking here. However it's only slightly dodgy to wetsand the fork's clearcoat down to a dull finish, primer, paint, and clear again. YMMV, YTMKO (your teeth may knock out).