Foxfire,
You actually cannot book a WDW wedding far in advance. The earliest you can reserve a date is 12 months out, and you sign a contract and get assigned to a coordinator at the 8 month mark. If there are many couples wanting the same date, same locations, time, etc., they will hold a "lottery". But, there are so many different locations, that a lottery isn't very likely. We were married on a Sunday, and were actually the only ceremony held at the wedding pavilion that day (they can do 5 or 6 per day). If I remember correctly, our reception was also the only one at the Grand Floridian that day too.
You can meet a sales manager as far in advance as you'd like, they can go over all the preliminary stuff with you, such as different things you can have, looking at locations, etc, it's just the date that you cannot actually reserve until 1 year out.
The fact that a coordinator was included was priceless to us, as we were planning our wedding from NY. It was nice to be able to call or email her with anything we needed, any changes we needed to make, etc., it took any stress out of planning a wedding from far away.
There is also an unofficial site dedicated to WDW weddings, it's a place you can talk with others who have had, or are currently planning a WDW wedding. We found it very helpful during our planning, and even if you're not planning on getting married for a while, it's a good place to ask questions and gather information before you make a decision. The website is
http://www.yourfairytale.com/mailist.html