I worry about the retrofitted rear suspension. I always recommend people to stick with the SLS (self levelling system) and put the $$ into fixing it on the wagon, its only the 2 shocks, 2 nitrogen cells or the SLS actuating valve that go bad. If you pile 5 people in the car does it still ride level and can you add 300 lbs of cargo and still not bottom out with conventional shocks? I doubt it. Anyhow the other thing is the aluminum head that tends to crack and fail, as well as a head gasket every few 100K miles that fails. And the AC can be very expensive to fix in the 124 chassis (or just about any chassis these days!)
Other than that, if there's no rust then fix it up and you should have one of the best running dieselturbos around, with excellent handling and safety features to boot. These were what, $40K new? About 2 years ago I was lucky and found a very clean '87 300D with 226K on it that actually had a working AC and a newly rebuilt transmission for $2500, it just so happened to need $3K of engine work. But its a great car now!
The one you are considering is worth maybe $1K depending on interior, if thats trashed forget it.

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!