I have a vinyl cutter in my shop that I use for paint masks, decals, headstock logo's, ect... Here is how I approach a full body decal:
I take a straight on digital pic of the guitar body. I then trace it in a CAD software, edit the desired image to fit in the outline of the body, cut the decal, and apply it. The application is best done with a mist of water on the body & on the sticky side of the decal (this will give you the ability to "float" it into position). Squeegee it out, and on to clear coat, and you are done.
If you plan on clearing over top of the decal, I would shy away from "printed vinyl" decals. They dont wear very well, And, some clear coats can smear the ink. You may be able to get a sample piece to see how it holds up to clear coats. Hope that helps....
BTW- Not everyone on the forum checks every topic on a daily basis. There is a lot of knowledge & experience on PG. A little more patients, and a little less sarcasm would probably get you more replies.