Both my sister's and mine had cracked, so I replaced hers first (waiting on a battery replacement, not using hers a a guinea pig) and it worked like a charm with no conflicts. Mine, however, should have been a much easier replacement because of the way it broke, but instead I got this white screen. I did a hard reset by holding sleep and home and it worked after a bit. Here is the video I did it from:
http://www.youtube.com/watch?v=dgcmZa5dCNo
And for anyone wanting to know how to revert the firmware, here is a website with the downloads (tested and works - at least it did six months ago):
http://www.felixbruns.de/iPod/firmware/
Simply plug in your device and hold shift and press restore, a dialog box should appear asking you for the file location, select it, and it should work.