Hi, I'm about to buy an iphone of a family member. The touch screen is broke on it but I can get one of ebay and I've seen how to replace them on youtube. All I wanna know really is, how do you find out what Generation it is, so I can get the right screen. And whats the general shelf life on them. She has had it for about a year and she bought it off her friend, so I dont want to be getting it then goes on the blink after about a month or so.