I got some expanding foam on my sheet metal just recently, and was able to get it all off very easily with a plastic scraper (one for teflon coated pans from pampered chef, just don't let your wife know... ) once it had cured. A quick buff and wax and you would never know it ever happened...
Last I looked into getting a tailgate repainted (different color) it was over $300; I was able to score a mint condition tailgate in the color I was looking for for $200. The choice was easy. Now I have a spare tailgate...