If you have pets, consider replacing the carpeting before putting your home on the market. Many people are allergic to pets and extremely sensitive to pet odors, which even a recent, thorough cleaning may not mask. And worn carpeting, even if it is clean, can detract from a home's overall appearance, giving the impression it has not been well maintained.
Bumper stickers and dealer emblems are usually attached to a car with glue. The best way to loosen glue is heat, so try heating it up with a hair dryer. Use a putty knife, with its blade wrapped in duct tape to work the label up as the glue warms up.