I dropped my iPhone and cracked the front and rear glass panels.
The repair went fine but took longer than expected. It took me a little over two hours to replace both panels. The instructions were very well written and easy to follow. If I have to do it again I'll be back!
The screws are really small, make sure that there is a method used to place all the screws/parts removed so that they can be put back in the same location. I used a white paper towel and positioned everything removed so that it was easy to assemble.
iPhone 4S Screen
iPhone 4S Blank Rear Glass Panel
iFixit iPhone 4 and 4S Screen Protector