1995 has the OM606 non-turbo in the W124 chassis.
1996 has the OM606 non-turbo in the W210 chassis with 4 speed transmission.
1997 has the OM606 non-turbo in the W210 chassis with 5 speed electronically controlled 722.6 transmission.
1998 & 1999 are OM606 turbo / W210 / 722.6.

How hard they are to work on is a matter of opinion. They do tend to go through glow plugs and plastic fuel lines pretty quickly. The intake manifold has to come off to get to the glow plugs, but that isn't as big a deal as the dealer service dept. makes it out to be. There's been lots more information posted - just search in this section for "E300."

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Rick Miley
2014 Tesla Model S
2018 Tesla Model 3
2017 Nissan LEAF
Former MB: 99 E300, 86 190E 2.3, 87 300E, 80 240D, 82 204D Euro
Chain Elongation References