I've only done one set of decals, and I won't do it for someone else, but....
The issue I would have with you doing the prep work and me doing the decals is that a lot of the final quality comes from a properly prepared surface. If you don't do it well, and I put the decals over it, you'll say that I did an ass job.
The decals literally take an evening to install once the prep work is done, they are pretty damn easy.