I can confirm as an owner of several W124 vehicles, most notably the 1987 North American market S124, this is the 300 TDT, a station wagon version of the W124 chassis with the OM603 turbo diesel. Currently my wagons clock has just over 370,000 mi. This is a unicorn car in North America. They only sold this car during one sales year in 1987, with this particular engine configuration. This engine can also be found in several other cars around the same era from Mercedes-Benz.

I also own a 1999 W210 with the OM606 turbo diesel. This is the electronically controlled and upgraded version of the OM603. I can confirm that the w w210 is plagued with the myriad of problems. But it is still a fairly nice chassis with modern features and once one becomes acustomized with its particular idiosyncrasies it isn't really that horrible. But it's definitely not the tank that the w124 and w123 series chassis were. The primary prize is the OM606 engine. Which is commonly extracted from the W210 chassis and used to repower any number of other vehicles. There are lots of ways to crank tons of horsepower out of these engines, but at the sacrifice of their longevity.