Broken screen repair for IPhone 4?

[karenhamer]

My wife had her iPhone 4 slip out of a pocket this evening and land screen first in the street. The screen pretty much shattered although the phone is still in perfect working order. Any idea how much it costs to get a new one put on by Apple? If we repair though them would it affect the warranty? Fortunately we kept our old 3GS phones so she can use it while being repaired.