I think you'll be pleasantly surprised how easy it is. Heat the old decal with a hair dryer and peel away or just lay it on top I think it'll look great ! Just mark the top and bottom of the old sticker with tape so you place the new one in the same spot. Either way, the bike looks great.
lol.. hence why i havent done it yet. Stickers dont make the bike ride any better. Way better things to spend my time on (meaning I didnt get around to it today either). Maybe tomorrow.
I wouldn't use a scraper just a little patience - you don't want to scratch those beautiful lowers. Heat the old decal up with a hair dryer so the adhesive becomes pliable, start peeling at a corner. I find if you use a few drops of lighter fluid or Goo Gone as you peel it will further break down the adhesive. Once you've peeled the old decal off, use a rag and or the Goo Gone / Lighter fluid to rub the rest off. Both products are inexpensive between $3 - $10 and can be found at Canadian Tire.
I may try lighter fluid. Wonder if it has the same issue as alcohol though, which clouds the paint? Never found goo gone worked on decals. Tried it before. :/