The iPhone4S screen was demolished by a 2 year old.
The repair was one of the most tedious, but it really honed my ninja vision and dexterity skills.
Make sure to separate out all of your screws and parts as you go along. This helped me put it back together with record speed. Also get some tweezers and keep them by your side. It will prevent you from having to touch any parts, and don't hit the sides when taking out the funny bone!