I just want to report that I finally have replaced the air cells. The bouncy rears has been solved - what a difference it makes.

Lessons learned:
1. The MB cd mentions 11 mm as the tools needed. In reality I needed 13 mm for the (3) mounting bolts; 11 mm flair for the line from valve to air cell and 17 mm flair for the line from air cell to shocks.
2. There was an adapter between the aircell and the hose to the shocks. This adapter had a copper washer which I did not have. I had to reuse the copper washer. I would have replaced it with a new washer had I known...
3. Space very limited with my back on the garage floor, but was doable.

The old air cells that I replaced are MB parts with the MB logo. If I am not mistaken, these are the original air cells back in 1991, basing on a marking that reads "03 1"....