I done cracked my fancy cellphone screen. Gorilla glass my ass! (Although I hear gorillas are emotionally fragile...)
I used this video (http://www.youtube.com/watch?v=AZDAIgwbX...) as a guide (Dig the soothing English voice.) His time: around 22min. My time: around 2h30min... pretty much what I expected.
I used the ifixit home tech toolkit plus a heat gun and a guitar pick as tools. The most challenging part was removing the back plate... those plastic clips are tough to get off with the pry tools (one didn't make it... RIP... You're my boy blue!...). From there on it was pretty straight forward. No real surprises. Just be prepared to spend some time ungluing the battery and the USB board from the old screen. I used the heat gun on low in 30s intervals, holding it about a foot away from the phone, checking the battery periodically to make sure it didn't get too hot.
Patience and precision are key. Don't force anything and be patient with adhesives. The video is a pretty good guide otherwise. Also, you may have to improvise... I ended up using a regular size slot head screwdriver wrapped in a sandwich bag as a pry tool ... worked pretty well.