Here is a quick couple shots to show the shock replacement on my 1970 Mercedes 220D but should work pretty much the same on any W115 or W114 chassis. This is actually quick an easy DIY job that almost anyone could manage. The hardest part is probably jacked the car high enough to get the shocks in and out.
The top of the shock is accessible from the trunk. There is a little plastic cover (already off and on the floor) to be pulled off. Then there are two 17mm nuts. You can use a wrench or if you remove the plastic bit behind the rear seat you can make room for a socket wrench.
The nuts come off plus a big washer. There is a rubber bit inside the cup bit the comes off too (still in for this photo).
Two 17mm bolts hold the shock in from the bottom.
Once the two bolts are removed the shock slides out. You need a decent amount of clearance room underneath. Grab the shock and compress it a bit. New shock goes in. A second jack would be handy here to compress it enough while you put in the two bottom bolts. Then the rubber donut, washer and two nuts attach up top. Put the plastic cover on and all done. Make sure all the nuts and bolts are torqued down correctly. Easy.
Hard to see but the new to this car shock is now installed.