Yep!
First let me explain what I said above.
Almost without exception, the cheapest time to book a Disney cruise is the day, the hour, sometimes the minute the cruise is released. On new itineraries, I have seen rates jump $500 or more on that first day.
I always recommend booking the second you can.
Then if you are sailing Disney before that cruise, you can reshop it onboard. All you need to do is tell the agent onboard you have an existing reservation and you want to compare prices. The agent will compare the price you have to the onboard booking discount and let you know which is better.
If the onboard discount is better, he will take your information and rebook it for you.
They can usually transfer your old deposit over to the new reservation, although I have had them tell a client before that they couldn't and they had to charge the new deposit and refund the old. That's not correct by the way, so if they tell you that ask them to recheck.
If you booked through a travel agent, they will contact the travel agent to make sure they are okay with the rebooking.
That's it!
