Use a hair dryer to heat up the old decal some while you are peeling it off. That will also help to keep it from chipping into many pieces. Wipe the topper down with alcohol/water to clean it and apply the new decal. The hair dryer can also be used to heat the new decal a little so that you can squeegee it to a tighter grip. (I make signs here).
I just changed the decal on all my toppers. It was easy.
Apply hot, soapy water to old car topper decal. Peel off old one(my old ones just came right off in one piece). Wash and dry the blank car topper. Use a spray bottle of soapy water to apply layer directly onto the cartopper. Also spray the new decal front and back. Apply new decal onto cartopper and slide into the desired position. Squeegee water from under new decal until water is gone and there are no visible bubbles or creases in the new decal. Let dry and let it fly.
