Will my magic band already have my dining plan programmed into it when I get it?
It should. I always have the front desk check them when I check in at Resort.
Your MB is linked to your MDE account. When your reservation is activated you will be able to access the dining plan. It used to be that you had to go to the resort to activate the dining plan, but if you do on line check in, you may be able to eat before you go to the resort ( but it is best to go to resort first). It is not loaded on your MB in a way that you get them in the mail, and you get to wdw a few days early, and can use the credits. Make sense?