There's a 99% percent liklihood it's the shock. If you get under there and eyeball it, there's a chance it's the hydraulic line or a leak where the line enters the shock. In that case I would expect to see hydraulic fluid outside the strut too. But it appears to be coming down the upper part of the bellows boot, so is most likely leaking from the shock itself.

Not much chance it's the accumulator, they are a distance away from the shock.

If the accumulators are good (i.e. replaced in the last 7 years of so, ride not unreasonably hard), I would replace that one shock. If you don't know how old the accumulators are, I would replaced both them and the bad shock. Failed accumulators can cause this kind of damage to the shock.

Lots of folks ask about converting the suspension to a conventional setup, but I don't recall any ever doing it. The self leveling struts normally support a good bit of the weight of the car, so you'd hav to replace the springs in addition to the struts. And a normal pair of shocks (e.g. from a 124 sedan) won't just bolt up to the wagon. I'd guess your least expensive route is to repair what's already in place.

- JimY