I just finished this process. We will be sailing next June, and I called Disney to book. Got my room # thru them. Also placed my deposit at that time. Then, the next day, I called Costco travel to transfer everything over. They will send you a form to sign, you either can send it in thru snail mail, or email (have to be tech savvy, it needs to be in pdf form). Once that is sent in, you call Costco a few days later to confirm everything is all set. You will then have a new Costco reservation number. But you will also have a Disney reservation number, if you call Disney you can refer to that number if you want to ask them anything. But just know, if you need to make any changes to your reservation, you can only do it thru Costco, they own your reservation now. Doing this, I will be getting a $520.00 Costco gift card, once the cruise is done!