My iphone 4 screen smashed but still works?

My iphone slipped out of my pocket and fell flat onto the concrete. The screen smashed but the touch still works! We have a warranty with Apple but I've heard it might cost money still if they decide they can't fix it and just give me a new one? Is this true? Or will warranty cover everything? If they can fix it, how long will it take?

Depends, usually $199 to fix but with a warranty they will replace it with a refurbished iphone 4.
as long as no water damage and never jailbroke.

Warranty will cover everything. Just take it to Walmart or wherever you bought an just tell them it broke an the screen cracked, tell them you have warranty an if you can get an exchange an they should let you, good luck!

I suggest avoiding that hassle and just fixing it yourself. There are a ton of videos on YouTube walking you through it and its a pretty simple repair. The parts themselves vary in prices depending on the quality you get. I suggest getting the better quality ones though. They will likely run you a bit more (still under $50 though). I use these guys for most of my repairs and never had an issue with screen quality - http://www.strivemobile.com/iphone-4-screen-replacement-repair-parts. They also have color conversions and stuff if you are into that sort of thing. But in my opinion repair is the best and cheapest solution.