Changing the battery in iPod/iPhone? - 2

What's the deal with how to change the battery in an iPod? You bring it to a store then what? Do they change it right there, Because I don't really want them taking it with all of my data on it. I don;t know what these "Geniuses" are going to do with my personal info. I mean, yeah I have a passcode, but still.
Could someone fill me on on how that works.

And also, when the battery is swapped, do I have to put All the data back from iTunes, or is their any internal memory that can hold at least the iOS?

It seems no one has ever had their battery changed and are only interested in giving their opinion as to what they think some random person will care about. I'm not interested in your opinion of what you think might happen, or advice on what I should care about. Just actual knowledge of the matter itself.

The problem with the iPods is that they are soldered together unlike the iPhones which uses all screws. When an battery is remove from a iPod/iphone the data is not erased but I would still recommend backing up your device. I believe that apple will replace your battery right there but your best bet is to call them and make sure. Hope that helps.