My Itouch 4th Gen. screen has cracked. Will having warranty make a difference for the repair price?

The bottom half of my itouch 4th Gen. has cracked. Everything is still working fine, it's just the screen that is damaged. I have a warranty for my itouch and i was wondering if the repair price would be any different. Also where do i take it for repair? Do i just drop by my local apple store, and give it to them to repair it? How long will it take for repair? or will they just replace it?