One doesn't have to be an NRA member in order to become an NRA certified instructor. Training counselors can require membership for those who take their instructor course, but this isn't common and I don't see any mention of it on GOAL's web site. The instructor training isn't really specific to any state, but since most people who become NRA instructors around here want to get the Massachusetts state certification as well, we cover the necessary aspects of Massachusetts law that instructors will need to cover in their Massachusetts courses.
One doesn't need to be an expert shooters in order to become an instructor, but must be a competent shooter, good at working with people, and a fanatic about safety. John and Darius do a great job training at GOAL. I'm going to be offering another Home Firearm Safety/Basic Pistol instructor training course at the Westford Sportsmen's Club this spring, tentatively the last two weekends in March. Training for these certifications, regardless of who's running the course, requires a little over 20 hours. IIRC, John and Darius like to do it Friday afternoon through Sunday. while I prefer one Saturday and the following Saturday/Sunday.
The first day focuses on teaching methods and skills, as well as NRA policies and procedures. The rest of the time is devoted to the specific lesson plans that you'll be using to teach the NRA courses. In addition to discussing the specifics of the lessons, you'll also engage in exercises in presenting parts of the lessons and conducting various hands-on training exercises.
Most people start with the Home Firearm Safety and Basic Pistol courses, because those are the ones for which there is the most demand around here, due to licensing requirements. You can also become certified in Basic Rifle, Basic Shotgun, two different Personal Protection courses (in the home, and outside the home) and other areas. The two protection courses require certification in Basic Pistol as a prerequisite, and Outside the home also requires Inside the home.
If you've got any more questions about becoming a certified instructor in any discipline, feel free to PM me. I'll be posting the exact dates and times of my spring courses here as soon as they're finalized.
Ken