Cracked iPhone 5 Back Glass

I was hoping to solicit some advise from the forum.

I received my pre-order AT&T iPhone 5 yesterday after waiting patiently all week and have somehow already managed to drop it on the concrete in my driveway, scratch the front and back bezel pretty good and shatter the bottom glass panel on the back (I didn't even know that part was glass). I still had the plastic covering on the back and front that it shipped with, but it didn't seem to make a difference. I went over two years with my iPhone 4 without even a scratch on it.

As of right now I don't have the AT&T extra warranty service.

I am not clear what the best way to proceed is at this time and/or whether I should add the AT&T warranty service to my account before letting AT&T know about my screen (or whether there is a similar warranty through Apple?).

The phone is still usable, but I would obviously like to get a replacement, if possible, understanding of course that replacement devices probably won't be in stock for a few weeks.

I apologize to everyone in advance who may still be waiting for their phones to ship - I barely used the phone last night for fear or scuffing it only to have a freak accident occur this morning . . .