Top digital display knackered.

[Bernard Fishtrousers]

Old lurker/new poster with presumably an old question.

My instruments work, the warning lights illuminate, the lower mileage etc display works, but the top display appears to have missing horizontal lines to the point where it is unreadable.
There's a gazillion of these for sale on ebay, but
1; are they likely to be as screwed as the one I'm taking out?
2; my man with the spanners thinks the cluster may be coded to the car and a different example simply won't work?

Your advice will be welcomed.