I just purchased a used 108K 99 GS400. The screen on the system is sort of faded, and only the top of numbers show up. Kind of like a broken calulator. I did a search and could not come up with anything. The sound and all of the buttons on the Nak head unit are operational, its just the numbers and words are cut off at the bottom. Is this an easy fix or does it require me to get a whole new head unit?