Yeah what they said, I had a polyurethane lip and it was all messed up but then I left it in the sun for a couple days and it retained it's shape and I put it on. Check out my build thread if you're curious :P
I took out the rear seats (both top and bottom) but I kept the cargo cover, carpet, and the piece of wood that goes under the carpet and above the spare tire. I'll post a picture up tomorrow to show you, I think it looks pretty clean, imo.