Cracked screen

Mom wants a new iPhone, I found one one eBay for a good price but the top left of the screen has a small crack.

Any website suggestions on where and how I can have the screen replaced? Around how much does this cost to replace?

Thanks.

Cellular Accessories - 3G, Microsoft, BlackBerry, BenQ-Siemens, Samsung, Tools, Acer, SonyEricsson, Acc

Not sure if there is a better site, but its one that I know quite a few people use. Hope this helps!

Thank you so much.