Ipod touch screen/display problems

Hi, I have either a 3rd or 4th generation ipod touch. My sister found it at her job a while ago, and nobody ever claimed. It operates perfectly, it simply just does not display correctly.I plan on fixing it and am wondering, does anybody know exactly what the problem is with this ipod? The screen has no exterior physical damage, but there is black spot in the top left, the white bar on the left side, and 90% of the screen is dimmed. The only part that displays properly is the top half centimeter about 1.5 inches from the right side (you can see the line going through calendar, photos, and camera). Thanks for any help.