I heard there's a solution MB specifies to get rid of oil in the coolant. I urge you to pursue this because I heard the oil can significantly degrade rubber cooling hoses, shortening their life.

Head bolts do not need retorque after service.

Synthetic or regular oil is a personal choice. I use regular.

Otherwise it looks like the repair went well. If you don't mind my asking, how much did it cost without the head rebuild?

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95 E320 Cabriolet, 169K