I just graduated the Rangemaster Instructor Development class a couple months back. Excellent course for what it is, and at least half the class had no teaching aspirations beyond "Take Me to the Range" hosts. IMO, it's overkill for the "Take Me to The Range" purpose, certainly if your training resources are limited.
If you haven't already, browse Kathy's articles at Cornered Cat. She's worth a Facebook follow too.