Hard to replace
I've tried to replace the touch screen (only the glass). In eBay it's about 25$ or something like that.
It hard, very hard to replace. I've ended with a broken LCD, because when try to separate the glass from LCD, LCD broke.
For me, it's better to replace the whole screen, not only the glass. I've seen it for 51$ in eBay, but worth it.
Video on how to replace (as you can see, you need a dryer, and big ball, because phone gets VERY hot, and you're the whole time thinking you're going to melt it