Yes, you basically pay the difference between your ticket and the AP price.
Bring your existing MagicBand. You will link the AP to your account (or they'll do it for you) and your MagicBand will work. When you get back home, or even while you're there, you may find that you'll have a MagicBand "ready to customize" in your
MDE account. Go ahead and do that and they'll ship another to your home...that one will have a small Passholder clip that goes over the band and a parking/discount card. When you upgrade and activate your AP at Guest Relations, they will also give you a card indicating that you are a passholder that you can use for discounts and parking on your current trip.
Some of the most useful (to me) discounts:
- Free parking. If you're offsite, parking is $17/day. Parking savings can really add up fast.
- A discount in most theme park gift shops and World of Disney. I think its 10%...if you buy in any gift shop, always ask if there's a passholder discount. I've even used it for buying a soda or water bottle...in a gift shop. I don't think the outdoor wagons give the discount.
- Another potentially big one: If you eat at a lot of table service locations within Disney property, possessing an AP gives you the ability to purchase Tables in Wonderland...that's another $100(?), but then you get 20% off your meals for everyone in your party. I believe they add 18% gratuity back in, so I almost think of it as paying for the tip...but Tables in Wonderland can pay for itself pretty quickly. In our case, with four of us, TiW paid for itself with 3 to 5 table service meals.
- There's other discounts that you can read about with the link mentioned above, but the ones I listed were the ones I found most useful.