i booked my trip on january 1 of this year.
when the
free dining was announced in the spring, i called and had my ressie adjusted.
i had pre paid and my trip was in the free dining dates.
disney issued me a credit on my credit card and i received it posted on my cc account 4 weeks later.
only problem i had was this.
had to cancel original ressie, refund request put in , then rebook with a new code and had to put money down on that new ressie.
i put down $200 on the new one and then paid it off when the credit came through on my cc.
to answer your question, yes.
i did it and it was easy to take care of.
on a package, i think there is a time limit on when you can make changes without penalty. some packages require paid in full 30 days prior of arrival.
room only is a deposit and paid in full at time of check in.
talk to a cm for accurate info on deadlines.