Change shocks or accumulator on a 560 SEL

I'm a long time Mercedes lover, but only a recent owner of my "weekend drive" : 1987 560 SEL. It has 213,000 miles but it drives very good. The only problem I am having is when I drive, the rear of the car bounces too much, messing up the ride. I have looked into it, to replace the shocks (which are self leveling suspension) but I dont know if I should replace the accumulators first, since they're less expensive. An interesting "symptom" is that my rear sits much lower than the front of the car.
From anyone's experience, are the shocks gone, or the accumulators need to be changed? I searched the site, but not much help on this topic. CAn anyone give me advice, link, and/or supplier for these parts? So far I have my eyes on Bilstein.
I'm only 22, hoping to expand to my collection...