Go Here
This site offers instructions on how to remove your cluster and add white faced gauges. Forget the extra steps, remove the cluster and replace the dimmer switch/rheostat. It is located directly behind the dimming knob. You remove it with a little hand force or easier with a flathead screwdriver. I have an extra one for my 1987 300E, if it fits your car, I will sell it to you for $5. New is around $20