Have not replaced the rear shocks on my W140, but have replaced the fronts... they're very straightforward.
For the front (each shock):
There's a single stud/nut at the top accessible under the hood.
There's a single cross bolt/nut at the bottom holding the shock.
Make sure you jack the car up under the lower control arm so the coil spring stays somewhat compressed so the shock is not under any tension. Also, I found my lower shock bolt/nut had some sort of "Loctite-like" product on it... a little heat right on the nut made the job a lot easier.
I've attached a small pix that shows what the front shocks look like once they're out of the car...
Hope this helps.