I have the same fog light problems. The left fog light and the left amber side marker is not working. I checked the fuses under the hood, on the side of the dash and next to the battery but could not find the problem. Changed the bulb but nothing happened. no power found on the sockets.
Is it so difficult just for a fog light? maybe MB needs to learn from toyota or lexus??
But this is a great forum, thank you to all, I learned a lot and could save some money by DIY rather than bring it to the dealer.

Frank
97 E420