The OM606's are extremely reliable motors, but their main issues are glowplugs, glowplugs, and glowplugs.
Because of their dual-cam, 24-valve head, MB had to use exra-long glowplugs (prechambers are in the middle of the head); the glowplugs have a habit of sooting up and breaking upon removal....plenty of info about that around here. I've had one shear its nut off and get stuck, in my E300.
OM606 model data (in USA):
606.910 = '95 E300 Diesel (W124)
606.912 = '96-'97 E300 Diesel (W210)
606.962 = '98-'99 E300 Turbodiesel (W210)
The 606 was introduced here in the last year of the 124, then continued on for four years in the 210. Mercedes added an electronic 5-speed automatic in 1997, I believe.
140k is good mileage for a 1995.