Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
I'm fairly sure that you can update the address on your account but also give the Apple team a call. It hasn't shipped yet so don't worry too much.
 
I'm with /dev/toaster on this. If you call them and have a CSR fix it, you're far less likely to screw up and get yourself booted to the back of the line than if you try and fix it yourself. There's still plenty of time before these things ship, so it shouldn't be an issue.
 
I'm in the same boat but as this is a lot easier than the iPhone and you can change that one, I don't think it should be an issue.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.