You can get the screen assembly or you can get just the glass. I would highly recommend you get the assembly because just replacing the glass requires patience, steady hands, constant, liquid optical clear adhesive, and a UV light. Although the glass is significantly cheaper, there is a very large possibility that during the glass removal process, the LCD will crack.
Parts for the screen assembly run around $30-$40
The glass only you can get for around $5 but you will be needing the tools to remove the old glass and replace/cure the new one.