I would replace as much as you can while you have the engine out, definately would replace the pistons/rings/valves/timing chain/cam/rockers...these are high labor items that you might as well get done while its easy to do.

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1996 E320
2000 C230 Kompressor
1988 190e 2.3 - 225K miles, owned for 7 years. I cannot say enough good things about this car. Very well built, even at 225 it ran like new.