Do they backup/restore to move my stuff to the new one ? Also, what happens about wiping the old one clean of my data ?
Make sure you have a full backup of the phone before you go out to the apple store. Connect the phone and synch once with iTunes. Look in iTunes under Edit/Preferences/Devices and make sure there's a backup there from that synch time. Then go to the store and get the phone swapped. Then come home and restore the backup.
There is, I believe, an option to erase the old phone's private data right there on the phone itself. If not, you can do it there in the apple store by hooking it up to a computer. Talk to the tech and make sure to get that done before he walks off with it. I'm guessing they'd do that as a matter of course.
If you're really OCD, you can do all of the above on a laptop that you bring with you to the store.