Depending on how bad they are you may be in for a lot of work. On our 38 ft RV it took me about 10 hours total using the heat gun method. I used a plastic scraper to loosen the decals that I couldn't pull loose. Once you get the graphics off then you have to use mineral spirits to get the glue to come off and then clean with simple green or other soap to remove all the residue. Lots of elbow grease.
Do a search and look for someone's post where they used a 3m Graphic buffing wheel. It's much easier or hire a detailer to remove the graphics.