Best bet is to call Apple and they can change it no problem for you. Had this problem I think with the 6, 2 years ago.
Thanks! I just tried to "chat" with them about modifying an order and they gave me this back, "Rest assured your order has been received if it appears on Your Orders page. However, at this time, you cannot make changes to your order online. As you can imagine, we are more than a little busy from the excitement of our recent announcements. If you come back in a few hours, you’ll be able to update your order then." So I am guessing I just need to give it a little time and I will try again online and/or call.
Does anyone know how long it takes for it to get to the "preparing shipment" step? I think that is when you officially cannot edit an address any longer.