What @redterror117 said is a better option. Just try to ignore the scratches.
If you ''really'' want to fix this, then you can buy replacement touch screens off ebay fairly cheaply. From there you'll need a '00' phillips game bit (it needs to be tiny) to open up the system. Follow this guide to get it open to the point where you can exchange the touch screen.
[guide|25071]
Once you're able to get the lower LCD/touch screen out, just be careful prying the touchscreen from the LCD, it's usually held in place with a strong double-sided tape. Clean off any old adhesive and get ready to add the new stuff on. Once they're apart, take your new touchscreen and place it into the housing (after removing any protection on the new adhesive) and then sit your LCD into place. This should help you get the alignment just right. From there, follow the guide in reverse order.
If you do follow this advise, just take your time and be patient with it.