I have taken both Rick's course (shotgun), and GOAL's (HFS, BP) with Jon Green. Both are top-notch.
One thing to remember that if you take an NRA Instructor course, you're agreeing to teach their material, their way.
No "W" word; their system, their rules.
Not that I'm implying that you're a loose cannon, but there have been posters here, saying that they "augment" the NRA materials- that's not what you're supposed to do.
The other thing that you will find helpful is if you can assist an experienced Instructor, at least until you find your footing. There's a crapload of info; it's a long day. At our Club, we have a Training Team, with a core of every-timers and a bunch of when-I-canners (myself and my son included), so different faces can keep the class fresh, and so you, as the Instructor, don't get wiped out 2/3 of the way through.
Best of luck.