With 243K on the timing chain it would be in your best interest to go ahead and replace it along with the tensioner. As for the chain guide, do it. I just recently had a 420 SEL that someone replaced a chain and tensioner within 4K miles and the guide broke and as a result the engine had 6 bent valves. Believe me, if the guide breaks on a diesel you'll have more damage than that to deal with.

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ASE Master Technician, Lead Technician-Deutsch American Inc. Over 6 years of Import Service-specializing in German Automobiles.