Thanks for your response. One of my problems is that I don't know how to assess wear on a cam lobe and hopefully you can help me with this.

In searching the shop forum archives, it appears that the Mercedes shop procedure is to automatically replace the cam shaft, all rocker arms and all lash compensators. This is great, but obviously very costly. On the other hand, a Mercedes technician posted a discussion on the subject in which he said that in the field the cam shaft wasn't replaced unless there was evidence of wear on the suspected cam lobe, and only the suspected rocker arm was renewed. I couldn't find anything that gave instructions on how to assess wear on a cam lobe.

I have removed the valve cover on the side of the engine that is noisy and checked the cam lobes for any sign of roughness and they're all smooth. On the other hand, it's my understanding that you can't reach a conclusion without first removing the rocker arms.