To get a good working knowledge of firearms i like AGI. Not only is Bob strait on his teaching but his small sense of humor is the little extra lol. A lot of it does come from the books and experience yourself like others have said on other posts. but the main thing is to get that information and learn it. Wilson combat has a decent video course for gunsmithing also. as for a ffl or licensing or anything of that sort if you can fix the firearm in the time the customer is there you do not need a FFL. BUT if you plan on keeping the firearm OVERNIGHT you DO need a FFL.