Aye, it's disheartening I know but the fellows above are speaking the unvarnished truth. Altho' there are those that would have you think otherwise, 'distance learning' of a non-academic subject, the physical output of which is the movement of your own body, is something of a non-starter.
Even if you are diligent with your "Be A Ninja in Five Weeks" DVD set and apply yourself well, the first time you find yourself in front of an instructor you will almost certainly find that what you have spent so much time practising is wrong. You will then have to spend even more time 'unlearning' all the stuff your have trained into muscle memory.
So, at the end of the day, if you cannot get to an instructor then it is best to treat such things as books and DVD's on martial arts as material to fuel your interest rather than a means of actual study - if nothing else they will give you an idea of what you will have to learn when you start training.