Look here for some info on the Dining Plan:
http://www.allearsnet.com/pl/packages06a.htm
It's $37.99 for an adult/ $10.99 child. You must have a Disney package reserved and the Dining has to be added on before you arrive. I'm thinking my
travel agent said 5 days before, but I may be wrong. If you want to add Dining to your package, I'm sure all you need to do is call Disney. The Dining Plan goes on your room key, no vouchers. You might have a difficult time making your ADRs (advance dinner reservations) since many people make them as far out as 180 days before arrival. I just made one for turkey-day and had to take 9pm, which is really to late for us.
My family's giving it a try for the first time on our Nov/Dec trip.