of questions in a short email, but you have given yourself plenty of time to get answers and still have to have time to thoroughly plan your trip.
First tip - use the various boards on this site and others for information
* The resort board has summary for most resorts. There is a subboard where people track available discounts. allears.net also has a good summary for each resort.
Think about what is important to you; price, location, pool facilities, etc. For example we stayed at the Contemporary when our sone was three. Most of our touring time was at the Magic Kingdom or Epcot. Since he did a nap everyday, the access to the monorail really cut down our transit times to and from the parks.
* The restaurant boards has reviews of restaurants and people willing to give advice.
There are plenty of opinions available and often at odds but still worth reading. If you read why people do or do not like a particular place you can often judge if that issues is a problem for you.
Buy a guide and peruse. In my opinion The Unofficial Guide is the most comprehensive and thus the best for first timers. Many local libraries stock some guides so you can get a look for free there.
People vary on how they book their trips. Personally I plan my own but I enjoy that process. I compare package versus separate items, dining plan or not, resort deals and so on. I know some people use only travel agents and there are a number that are specialize in Disney. As I understand it Disney usually communicates deals and changes to travel agents before being released to the public. So it depends on how much work you want to put into it.
You can always book a room only with a AAA rate and change the reservation later. They sometimes run out of rooms for that lower rate. The amount of the discount varies by resort level and season.
Whether a non standard discount (rooms have rates by season) is available in December depends on when you go. The first three weeks or so will likely have discounts. Around Christmas (depending on the day of week) and through New Year's Day the parks are packed and a discount is unlikely. Last year December discounts were announced in August. The year before they came out in July. The far right tab on this site is for discounts. Disney also has a special offers link in the drop down menu for "Tickets & Packages" that outlines all current offerings.
In summary, I wouldn't worry about booking right away. Take a couple of months to familiarize yourself with some of the details about resorts, parks and tickets. Whether you plan the trip yourself or use a TA, understanding the basics on these will help you have a vacation that better fits what you really want to do and could save you money by not adding extraneous options.
Her is a link with room rates for this year.
http://www.mousesavers.com/roomrates2011.html