Im guessing that you'll get an identical model to the one you sent in.
They will probably be refurbished stock with a new battery.
I dug out my old one and ill let people know when I'm done with the whole exchange process.
Here is how to downgrade from iOS 5 to whatever the current non beta version is.
The first half of the guide is how to put it in DFU mode, and the second half is dealing with the "This device is not eligible for the requested...