Never ever pay more than you can get for parting out a non runner. Or another guideline is to consider the worse senario and allow for it in advance. That way there is usually no downside.

All problems are not cheap to repair by a long shot. If it is something simple you can be ahead of the game. There will also be the case where you do not luck in.

Then there is also the unethical seller type lurking out there as well. For example if I was an unethical seller and had a really bad engine knock. I would get more for a car by disabling the engine as someone would come along that would perhaps asume it is something simple. I know in advance with a pronounced knock present most buyers would reject the car.

At least have a look to make sure the timing chain is present on the top sprocket. A thrown chain may mean a replacement engine for example. Or the airfilter is not saturated with oil perhaps indicating a very worn engine.

All the above said it certainly could be something simple. Just not wise to bet on it. Also at the indicated milage the interior should still be pretty good. There are far too many mercedes diesels out there with the incorrect milage on the odometer. Just a few opinions and that is all they are.