I use Orbitz and Travelocity to do my research on hotel prices & amenities and then actually book the room thru the hotel site itself to see if they have better rates for AAA or the Entertainment card. I use Kayak.com, Orbitz and Travelocity to do my research on airfare and again I book thru the airline's website to save a few bucks on the fees the other sites charge. If you are going to get a rental car, then check out the codes on Mousesavers.com to see if you can get a discount on the car rental. And depending on how many days you are going and if you want Hopper passes(and if you are a member of AAA), then you can check out your local AAA office for their discounted tickets.
That said, I have been to WDW many times and have prior knowledge of how things work and where they are located in proximity to the parks. Being a first timer, you may want to consider using an agent to make your arrangements. They have the know-how and can guide you along the way. And from what I read, Kingdom Konsultants seems to be a great way to go.
Also, do yourself a favor and get one of the Disney Guidebooks. A little research ahead of time can really help you decide what will be best for you.