Forget the "kits", and just send me the money. Then go to the BATFE website. atf.gov is the site.
First, you must intend to "Engage in the business" of buying and selling guns in order to get an 01 Dealer's FFL.
Second, you must be in compliance with all state and local laws- like zoning, business license, etc etc.
Third- the class III thingy- you get an SOT- Special Occupational Tax, along with the 01 FFL. Think hard about that part. Expensive, limited customers, and the cost of a transferrable full auto firearm is enough to bankrupt a small business.
And where ARE my manners? Welcome to the forum- when you get a minute, stop by the intro thread, and say howdy. You also want to search some of the earlier threads where this has been discussed.