Norm, expect the estimate to be around $2,500 ... that's what our daughter paid 2 years ago for replacing the head gasket on a 1991 300CE. Only have a reputable, MB-trained indie perfom the work.

If you intend to keep the car longterm it would be a good idea to rework the head ... polish the valve seats, replace/regrind the valves and replace the valve stem seals.

It would also be a good idea to check the timing chain stretch and replace the upper and lower timing chain guides while the engine is apart. Depending on maintenance history you may want to replace the water pump and thermostat too.

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Fred Hoelzle