Repair of Ford Keycoe Radio Cassette?

I have a ford keycode radio cassette in my 1990 Ford sierra 1.6L.Although its working fine,the digital display no longer lights up.Im told I need a new Unit card to be soldered in place of the old unit,but cant find anywhere that repairs car radios anymore in my area.I do know the PIN number of the unit.
Maybe I could repair it myself,or if not get another Ford radio cassette to replace it with.
Many Thanks Paul