To add to Mike's excellent post, 5 cylinder Diesels were available in the US through the 1985 model year. These would include the (W123) 300D sedan, 300CD coupe and 300TD wagon as well as the (W116 and W126) 300SD sedan. I'm not sure if the coupe was available through 85.
The 300D sedan got a turbocharger in 82, the wagon got a turbocharger in 81. I think the coupe got a turbocharger in 82. The 300SD was avilable in the W116 body style (think 450SEL) from 78 - 80 and in the W126 body style (think 500SEL) from 81 - 85. All SDs are turbocharged.
Everything to this point has iron cylinder heads. Everything below has aluminum cylinder heads. One good thing about the aluminum cylinder head engines is that they have hydraulic valve adjusters that don't require periodic adjustment. A valve adjustment is otherwise required every 15,000 miles. It can be done at home or for around $100 at a shop.
3.0l 6 cylinder cars were available in 86 and 87. Basically you have a choice of the (W124) 300D sedan and 300TD wagon and the (W126) 300SDL. I'm not sure if the 300D and 300TD were available both years.
The 190D was available with a 2.2l 4 cylinder and 2.5l 5 cylinder. The 5 cylinder was available with and without a turbocharger. Manual transmission was only offered in the US in the 190 series.
MB Diesels were again available in the US from 90 - 99 with maybe a lapse in 94. Those cars are much quieter and much more sophisticated, but [I suppose] prone to more problems and as yet a good one for less than $10,000 is a rare find.
81 300SD - 292K miles