You definately want to take them off prior to prep. My 1985 Burro
decals were cracked and dry rotted, but came off easily with a heat gun, but be careful with the fiberglass. I also used the 3-M wheel as Raya recommended, to remove the excess glue residue and small portions of decal that tore while pulling it off. You will have to block sand the area where the decal is so that you will not see evidence of it after the paint
. I had to primer seal and block sand several times to remove all traces of the decal. The original gell coat weathers and looses thickness, but where the decal is, the gell coat is at its original thickness and after painting
, you will see the outline of the decal if you do not properly prep this area. If you are replacing the decal, then you don't have to worry about it as long as it is the same decal style and size.