The problem I forsee is unique information. What did you do that no one has ever done before? If you just slap 6hours of you building your cab and some plans on a dvd, I don't see many people buying it.
That is not meant to be a mean statement, but instead a genuine concern. You need to differentiate yourself from teh hundreds of pages of information available for free online. I can have wiring diagrams and cabinet plans downloaded in 5 mins. I can download artwork, read tutorials, and ask people here about problems. All of that adds up to me not considering buying a dvd with that info there... even if it is all neatly packaged in one disc. I think there is a market for it (albeit a small one), but you need to prove to everyone that you have something that NO ONE else has.. otherwise, most people will probably just stick to BYOAC and google.