I'm taking my iPhone 3GS to the Apple Store tomorrow to determine if my wifi is messed up (slow). If I do a backup of my iPhone before I leave the house, and if they give me a new device, can I restore onto that new device?
They will activate your phone for you, when you go home just plug in into itunes and restore from your back up.
What he ^^ said. When you plug it in you can select from which backup to restore from. Restore from whatever you named your current phone and the latest date a backup was taken. I'm actually doing it right now, coming up on an hour long process thus far....