I understand it is possible to apply an annual passholder discount to a room/dining package - if the package AND the discount are available for the dates and resort you want.
Your reservation would be a package and it would be subject to the same deposit, change and cancellation rules as other packages.
I don't even use the DDP and I have never booked one of these packages, so I am not sure what the change rules are. But I believe the deposit is $200, and there is a penalty for cancelling the reservation within 45 days of arrival.