Those decals sound amazing, i really need to buy a printer so that I can make my own! What kind of printer do you need? I tried printing some with my home printer, but they just wiped off the decal paper.
Re the wheels, you DEFINITELY want to use the kit ones I think. There is a rather elaborate (but very nice) tool for making them because the spokes don't sit flat, they are angled. You'll see what I mean.
The issue comes when you put the two sides together - in my case they didn't sit flush, so there was a thin gap. Very easy to fix - just a bit of filler, sanding, and then another coat of paint over the top. Maybe you'll do a better job getting the two halves to fit - the issue for me was that i did not get the top of all the metal spokes to sit perflectly flush inside the rims.