It's thought easier to replace the whole speedo complete not the display your last or cars last mot should have a record of the mileage, you buy a secondhand unit from say ebay plug in and use a computer to set it up with the car, you can increase the recorded mileage but not decrease it so if your car had 88k on buy one with a reading almost the same or lower, if you go the repair route use a professional service obtaining only the lcd seems an issue