Decal removal with a hair dryer is not too bad as long as the decals are not dried and cracked. If they are then it becomes a cumbersome chore to the point that the eraser wheel is about all that will work. The wheel does not last as long as I expected and throws off a lot of rubber crumbs that look like sawdust.
I used all those techniques on mine. Some sections came off quite nicely with a heat gun and a scraper but the cracked sections were a real PITA! I noticed the dark blue decals were not cracked and dry like the black and dark gray ones. The blue came off fairly easy but the black did not.
The yellow decals came off in two sections, first the yellow colored vinyl peeled off and left behind a rubbery gray substrate which had to be removed with acetone. I had to use the eraser wheel on most of the black/gray.
YES! The decals are installed before the windows and doors. I know this as I had to remove several due to water intrusion damage and found the decals went right up to the edge of the cutout.