My spare header has some cracks and pock marks, assuming from rocks, but isn't outright missing portions like my current one. i want to make this car a good 10 footer, so what are the materials i'll need, down to grits of sandpaper, to fully refurb the header? Is there a special filler i need for it? I know its not fiberglass, it's that pressed matt stuff right? Complete novice in bodywork.