I have an iPhone 5S that I dropped. The right half of the screen is unresponsive to touch, so I want to replace the screen. I have never replaced a screen before, and I'm looking at used iPhone 5S's on ebay. Is the top glass part of the screen too? Or can I keep my glass but only replace what's under the glass? I'm asking because I see some used iPhones where people say their screen has scratches. My screen is cosmetically fine.