Good choice,
I built my tail kit at Synergy Air. It was a good program, well worth the cost.
Have you planned how to get the tail home? It will more than fill a 8ft bed full size pickup and you will not be able to shut either the tail gate or cap door in the rain on a dark and stormy night ( Don't ask how I know).
They also have a Quickbuild class, also very good. However, I took it way too soon. If my experience is typical, take your estimate of time to build, then double it once or twice, then schedule the class.