I'm going to be getting the head gasket on my '89 300CE replaced. I've done some research on the M103 engine and its various faults, but I'm wondering if I need to do more extensive work when I have the head off. Firstly, i understand that valve guides and seals are a weak spot on the M103. Is it advisable to replace the valve guides, even if they are within factory specs? The car currently has 100k km (62 000 miles) and exhibits no significant amount of oil consumption besides the small amounts seeping from the leaking head gasket. Secondly, I understand that the timing chain and the timing chain cover are known to cause problems, I would imagine that the timing chain cover gasket would be replaced with the head off, but what about the chain. Is it advisable to change it at this time? Previous threads indicate that the relative ease of changing the chain while the head is off makes it all the more worthwhile to have replaced, but I'm wondering if this is overkill considering the car's low mileage. Is there anything else that should be considered when doing this job?