My door over the gas cap just fell off. It appears the plastic hinge has broken and needs to be replaced on the door. But it appears to be riveted - I can't figure out how to get the old one off and the new one on. Any advice?

Also, I had the unfortunate problem of falling asleep at the wheel and my car ran into the ditch - with cruise still on. Flew threw the deep grass for a bit before coming to a stop. Car did not "appear" to have any damage, but I'm a little nervous driving it, thinking how could it not have damage. Any advice on what might have happened to the undercarriage (if anything) and what to look for?

Thanks