Thanks primarily to Dwight Hinton's advice, my startup clatter has been fixed. My local dealer is Mercedes Benz of South Bay. Large as it is, they had no knowledge of the service bulletin that Dwight references on the "500E owner Roll Call" thread. Nevertheless, they were inquisitive and responsive, and when I brought my car in, along with printed diagrams of the oil filter housing showing the check valve, the notes from Dwight regarding the check valve upgrade, and basically a diagnosis and solution path for them to follow, they got right on board.
Note the same dealer replaced the timing chain a few thousand miles before. They were unable to get a copy of the service bulletin (which they described as an internal document and were mildly surprised that I had the number for them). Nevertheless, when they pulled the oil filter housing, they found the old style check valve, and had the newer-style part in stock. Result: start-up clatter is GONE, and lifter noise when cold is GREATLY REDUCED. It cost me about 315 bucks.
Thank you all! I love this place!!!
1995 E320 Wagon Moonstone Grey/Parchment 106K mi.
2007 E63 AMG Graphite/designo 75K mi