4) The premium you pay for a Diesel car these days means a lot of miles before a Diesel makes better economic sense than a comparable gasser. Consider that a typcial 96 E300d costs $12,000 vs a similar 96 E320 at $8,000. How many miles/years before you make up $4000? Not to mention you have your choice of E320s vs the two or three 200K mile E300d's available to you.
5) The 90s E-class (124 and 210) are steps above the 123 in refinement and IMO worthy successors to the 123. I don't think you can push a wagon as hard as you can push a sedan but you probably wouldn't drive that way with a full load.
6) Diesels were sold in the US in the 95-99 model years. No Diesel wagons in those years. Possibly no wagon in 96.
7) The 98-99 E300 turbodiesel is a heck of a ride

Talk to experts about the propensity of 96-up cars to have front suspension towers come apart from corossion. I don't know if that means 96-99 cars should be avoided in your situation. If you're thinking Diesel, I'll not go into the V8 and AMG versions. If you get a later car, definitely go for Xenon headlights.
Sixto
93 300SD