I'm replacing the wing mirror covers on the A4 with new matte chrome. I've managed to do one luckily since one screw was fine and the head snapped from the other so the plastic under piece still managed to pop off. But the underneath screws on the remaining one are completely wrecked. Too much rust has ruined the heads so I can't even attempt to loosen them. I have no idea how to get them out. Any solutions? Is it possible at all to replace the top casing without taking the screws out?