Robert Dunlap is the fellow who shows up on those AGI tapes. He's one of those old timers who can really work on Colt Pythons. While he is very knowledgeable and has years of teaching at Lassen College (& the NRA Summer Schools) behind him, I am very skeptical of how-to tapes which are only 90 minutes in duration. In all fairness, I have yet to view a tape.
Any NRA class would run about 1 week long (over 40 hours) and to expect a video to give you the equivalent in training is not realistic. Besides, the camaraderie of crawling around the floor looking for a lost part can't be enjoyed on video. Maybe the classes were 30 hours of crawling and 10 hours of gunsmithing. More seriously, Small Arms of the World will tell you how to disassemble virtually any gun out there and I'd rather buy a Jerry Kuhnhasen book or go back to school than buy a video.