Bring your original box if you want to swap it out.
Make sure you do a restore first (or they will not swap it out and will either send you home to do a restore or make you do one in the store and then send you home.... you will have to make another appointment to swap out.)
Also, make an appointment at the genius bar before going to the store as, chances are, you will be turned away without an appointment.
Just tips from my experience.