My wife and I are going Thanksgiving, so we're going at a similar time as you. We booked a while ago, but we just added the dining plan, and set up our Magical Express arrangements through the main WDW customer service line. We also went ahead and set up Advanced Dining Reservations for most of our dinners. We've been to WDW a few times though, so we knew where we wanted to go and how we like to break our days up. Some people don't like having a pre-planned schedule, and therefore don't like to make ADR's prior to their trip, but we figure, worst case, we cancel the ADR later. It's much easier to cancel an ADR you don't want, than to get one at a place that's no longer taking them.
In terms of the dining plan. Whether it is a good idea for you depends on the type of dining you're interested in doing, and mainly, whether you would ordinarily use the number of sit down meals on the plan. At a nice sit down restaurant like Le Cellier, you would easily drop $40 per person on a meal. At the lower tier, like Sci-Fi Diner, probably $20-25. A counter service meal usually will cost you at least $9-10 per person, and then the snack gets you a snack up to $4 in value. So even if you only ate at lower tiered sit down places for dinner, you would be breaking even, but knowing you can eat at much nicer places, is where the package is a steal. My wife and I looked at the menus of the places we wanted to eat and found we were each getting $100 - $150 in value from the plan, and didn't feel like it was forcing us to overeat or anything. I mean, coffee and bagel for breakfast, sandwich and chips for lunch, and then nice dinner isn't really all that much food if it's spread out. But if you really would ordinarily only be eating quick service meals, then the package is not for you.
It depends on what you're interested in, but we also bought tickets for the Very Merry X-Mas Party at Magic Kingdom. You can check the website to find out what days they'll be doing it during your stay. The tickets ARE a little pricey, but we figured it was such a unique experience, with snow on main street and all sorts of X-Mas decor and caroling, etc., that we couldn't pass up the opportunity. I don't know how fast these tickets go. You may be able to still buy them after you arrive, but we didn't want to risk it.
We're also planning on going to Epcot's Candlelight Processional. It may not be necessary, but we're planning on booking a dinner reservation at Le Cellier in the Canada section of Epcot that comes with a reserved seat at the Processional. It's a prix fixe dinner that's normally $47, but you can buy it with the dining plan, which is a great deal. Last time we called WDW they said they would start accepting those reservations in August some time.
In terms of when you get stuff - the only things we've received are our confirmation letter after booking our trip, and the X-Mas Party tix. Usually about a month or so prior to your trip, you'll receive a package with your luggage tags, all your trip details and some brochures and stuff.
Other than that, you just wait. And wait, and wait, and wait. I downloaded a widget for my Mac that is counting down the days, hours, minutes and seconds until our flight. 129 days, 19 hours, 3 minutes, and 22 seconds and counting...
