I removed the stickers off of my Trophy last week. I had tried earlier when the weather was cold, and found it difficult so heat does help. The gray/silver shadow areas were the most difficult. It took about 2hrs. per side to get all of them removed. I did compound and wax one side after removing the stickers and it seem to make things worse. You can see where the stickers were more on that side than you can on the other side that I did nothing to.
I have never pulled thevinyl graphics from a boat, but we just striped the vinyl off our motorhome to put new graphic on. The best way I found was use a blow dryer on a warm day. The vinyl and glue come off together. Mineral spirits is good for removing any remaining residue.
As far as the color difference, that is the work of the Sun, I haven't found anything to change that. The folks that replaced my graphics said it will blend with time.
That bottle of decal remover at walmart works pretty good. Buy a couple of bottles because you can always use more. Rub it on leave it for a bit then come back with a razor blade or plastic putty knife.Work in small areas and it comes up real good.Wipe the area down with some more of the stuff to get up any residue, then use some hull cleaner and blend it in or do the whole side. It worked pretty good on my old river boat those decals had been on for thirty years, this left no imprint. This stuff is probably very similar to lighter fluid.