They are a pain to get off! Mine were peeling at the top when I bought the truck used. I found that parking the truck in the hot sun was about the best bet (even better than a heat gun in this case). I used some Eastwood nylon scrapers to get under the edges and peeled VERY slowly. I then used the Eastwood adhesive remover (my trusty 3M adhesive remover didn't even touch whatever they used to glue these things on!). After I got everything off I used DC Car Care's (Don) glaze polish to put a great shine on the paint that had been hiding behind the stickers.
After all that work I drove it out of the garage, took a few steps back, and decided that I liked the way it looked. If I ever get around to making it black again I'll probably take it to the Line-X dealer that did my rocker panels and bedliner. That way I'll never have to worry about the wife's rings scratching the paint when she closes the door!
I just couldn't imagine getting those stickers off and then turn right back around and put new ones on. That's just me though, good luck with whatever you do.