I have broken my LCD screen for O2 atom before and went through the horrible same pain of only being able to receive the phone call and calling the last person who you previously talked to.
Getting a new LCD screen is easy. Now, there are many sellers on eBay who sells new LCD screens. However, one of the hardest part was to find out how to change it.
Believe it or not, O2 is one of the most easiest handset to dissemble. I found my guide on google which was in chinese, however, the pictures themselves were pretty much self explanatory.
Hope this helps.