You take the cluster out of the car, take off the back cover, flip it over, drill some holes to gain access to the screws to take it apart further, and get to the ribbon strip assembly. It's a pain in the ass if you don't know what you're doing, so I suggest sending it to a repair company like VDOrepair.com if you don't feel comfortable ripping apart your gauge cluster.

FYI....I'm fixing mine this weekend by replacing the ribbon strip. I'll snap some pictures.