If you can afford it and would find it valuable, I would hire a guide right from WDW, but I cannot stress enough that I don't think that's neccessary, no matter how much money you have. Birnbaums and the UnOfficial Guide are more than enough to help you! I buy them even though I've been 13 times just because there's new stuff all the time, but mostly b/c it's just another way to get me psyched for my trip!
If it really will make you feel more comfortable, do it, but I think between the aforementioned books and this site, you'll be fine.