If you go through CRO (Central Reservation Office) (407-934-7639) they will require a one night deposit, with balance due at check in, and there will be no time limit on modifications if you decide to upgrade or apply a code later. Your confirmation number will have 12 digits in it. Be sure to ask for a room only.
The Disney Travel Comapny will require a $200.00 deposit, balance due in 45 days, cancellations cost $100.00 and modifications <45 days will cost $50.00. Your confirmation # with DTC would have 8 digit confirmation number. DTC will also try to add something in, so that it is a package.
I would definitely go with CRO and ask for the cheapest room in whatever category you want. They will not tell you if a code is available for that room unless you ask.