I want to either fiberglass or paint my dash...

I have a 94' s-10. I want to either fiberglass or paint my dash and my door panels. I have never fiberglassed before but I think after reading I can figure it out. I have sanded an interior before to be painted. My real question is: If I fiberglass my dash and door panels can I just use the originals and do the fiberglass over it? What's the best way to do all of this?