Repairing a Roland XP-10

I got this very dirty Roland XP-10 at the same garage sale as the Casio WK-1800 I showed a couple of months ago. The price was the same, 100dkr, which is way lower than the usual asking price for an XP-10. I turned out that there was a serious problem with it: The display was unreadable so I had to find a way to repair it. The music is a combination of manual playing and MIDI file. The first song is 'Orient Express' by Jean Michel Jarre which is mostly a MIDI file, the second is the old Dollar hit 'Mirror mirror' and here only the rhythm is MIDI. Both songs are played on the Roland XP-10.