I haven't done it, yet. I've read all about it though, so I guess I'm an armchair/internet subject matter expert. LOL
Anyway there seems to be several choices for removal. 3M makes a "removal wheel" that attaches to your drill. Reported to work pretty good. Amazon has them.
Others have used a razor blade and heat. I would be very careful with the razor blade. You can get a heat gun from Harbor Freight pretty cheap.
Another option is using a wallpaper steamer. There is a current thread about that on RV.net, I think in the 5th wheel forum.
3M makes aerosol "Adhesive Remover". I would test it in a small spot first.
I've been saying for 2 years I was going to do it on my cabover. I think the biggest problem is ghosting. You will have as new fiberglass under the decal as opposed to weathered siding everywhere else. Look on that RV.net thread at what was done. Used a wallpaper steamer, then masked and painted with Krylon.
https://www.rv.net/forum/index.cfm/f...g/1/page/1.cfm