I used this webpage below to remove my R170 dash and replace a couple of bulbs. Good instructions and pictures. Takes about an hour. The only semi difficult part is removng the key trim. There are two small locking tabs (top and bottom, right behind the trim) which need to be lifted to remove. Here's the bulbs you need:
0015445594 Instrument Light; Clear Push-In Bulb; 12V/2W Buy at least 2
62111391260 Instrument Light; Instrument/Dash Bulb with Beige Socket Base; 12V/1.5W (2452MFX6) Buy a half dozen
I purchased at Autohaus AZ. I replaced all of the Tach, Speedo and Gauge lights. Bulbs are cheap, so replace more than the broken bulb.