Hah, you beat me, I spent $4500 on mine!
Bounce the rear end -- if the suspension isn't soft, you need new accumulators for the self leveling rear end. This is important, as when they go completely flat, the struts get pounded to death and the cost the earth. Ride should be glassy smooth with two adults in the rear.
Replace the front flex disk, too, it's probably bad if the rear is.
Check the links on the rear suspension, at this milage they may be wearing. The rubber on the bushings (vulcanized in place) will tear and shred. If any are bad, expect to replace them all.
Check the rear diff mounts, probably also gone, causes thumps when shifting.
All the rubber hoses in the engine compartment are likely rock hard and leaking unless previously replaced, including the idle control valve hoses.
Nothing else particularly specific to the wagon, everything else is typical of a W124, including the maddening leaking AC evaporater.
I've replaced all the rubber in the engine compartment, a water pump (at 218,000 miles!), the accumlators in the rear, and need to do the flex disk and evaporator this winter. Else trouble free except for a fan clutch and new radiator cap.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!