How to Fix iphone 3g screen (grey area)

[madxface]

Guys, I need help with fixing my screen. What should I buy? just screen, or screen with digitizer or something else.
I am not sure with this grey area (yes, it's still sensitive to touch and fully working)
thanks

https://fbcdn-sphotos-a.akamaihd.ne...3427722609_1482407203_3156667_720903427_n.jpg