About a month after the warranty on my SLK 230 ended, the dash light for one of the heater controls went out. It's easy to replace. Just pull the knob off and there's a tiny grain of wheat bulb behind the knob. I used two tiny screw drivers to get the old bulb out. The replacement bulb just pops in.
I got the replacement bulb for about $1 at CarQuest. Its brightness is identical to the original Mercedes bulb.