We bought a MYW ticket from AAA and want to upgrade to an AP with the DVC discount once we get down there. Will they simply subtract the price we paid at AAA from the price of the AP (with discount)? I tried to email Disney with this question and got a very vague response that said "All ticket upgrades must be done in person. Please present your tickets at any theme park Guest Relations window for assistance. Some variables may determine if an upgrade is possible." I'm not sure what the 'some variables' would be... that's what made me nervous.