The good news with regard to removing permanent marker from a metal surface is that it is easier to remove Sharpie from nonporous surfaces. This is a guide about removing permanent ink (Sharpie) from metal.
In a hidden place take the sharpie and make a mark, let it dry then write over the mark again and quickly wipe both marks. The new ink should remove the old. You may have to do this more than once. If it satisfies you here, go to the real mark you need to remove and repeat without letting the ink dry. Also try nail polish remover, again in a hidden place always when experimenting.