The wiring issue was cured in 95 or so , the W210 E class you are looking at came around in 96.

Wagons have a rear Self Leveling Suspension. This consists of hydraulic cylinders, accumulators , leveling valve and 2 section power steering pump.

This can get expense to fix once you get much past replacing accumulators. You could use springs from a sedan and some adapters to mount standard shocks in place of the SLS rams. Some advise against this, the only real reason wagons has the SLS was to deal with varying rear loads not typically found in a sedan. If you don't wildly load the wagon, it won't be an issue. ( I'd use the thickest spring spacer to deal with the slightly heavier static wagon weight / possible cargo loading )

The other issue with the W210 is rust, front upper spring mounts rust away, fenders and doors get rusty.

No matter what car you want to buy, have a mechanic look at the car first. Most Mercedes age well having good interiors / paint but can get just as rusty underneath as any other car.