560SEL: rear sus. sags AND has a stiff ride (also Q about alternator replacement...)

[WANT '71 280SEL]

Second time typing this becasue I'm having some problems with my internet that not everything gets sent, sooooo.... here it goes.

Looking into a 560SEL. Haven't been told what year but know it has 165k miles on it and no rust, so I'm drooling. The owner's friend is a member here, thus how I found out about it.
He thought it need rear airbags. Not possible really since it has a hydraulic, not an air suspension like the older m-100's. I have read extensively, and have come to the conclusion that the accumulators are bad causing the stiff ride. BUT, people who had bad accumulators never said anything about sagging rear-ends. One person said that when his were bad, the car was still level. What do you people think would cause it to sag? WOuld it most likely be something simple such as the arm needs adjustment that is on the rear sway bar that triggers it to raise and lower the rear-end?

One more question, the car aslo needs an alternator. Since it is so far away I wanted to have it shipped, but was maybe wondering about me just doing it there? Would it be simple enough to do that? Exactly what tools would I need? Is it setup just like a 420SEL alternator wise such as belt being in the back so every other belt has to come off to get it?
Thanks
David