After pricing the local repair shops for the price of installation($300 to $400) and cost of four new Bilstein shocks (up to $520 for the four), and counting the total number of bolts involved (four each on each of the front struts, two each on the rear shocks, I purchased four heavy duty stocks via mail order and installed them all by myself on my 1990 300D (model 124) My delivered cost was $400.95.
I am a 60 year old Spanish professor with a cold and a case of mild arthritis. The job took me a total of 6 hours, most of it used in removing the front struts (the bolts were very firmly attached) and finagling the rear shock into position for lining up the bolt.
You will not need spring compressor. You will need 10 and 17 and a 19 mm sockets and 1 7mm hexkey or hexkey socket and rachet, a jackstand, a bottle jack or two and 17mm, 19mm and a 22mm boxend/andor open end wrench, and of course, some WD 40 and an appropriate assortment of German swearwords.
I started by removing the front wheel and seting it on a nice red jackstand then squirting WD40 on the two lower bolts and the transversal upper bolt. You will get nice shiny new bolts from Herr Bilstein. Then set a jack toped with a block opf wood on a bottle jack under the arm, so the spring will not extend itself and harm you once you have unbolted the strut bolts.
Then I removed the two 19mm bolts connecting the steering knuckle to the strut (a footlong tube from the bottlejack provided extra leverage: I hear Herr Horst Niebelungen at the MB factory was a weightlifter back in 1990 and it was rather permanently attached. The transversal 17mm bolt was also rather hard to turn at first. Put one wrench on the back and turn it with the rachet or a second boxend or openend wrench. The nut in the engine compartment is a 22mm nut with a shaft with a 7mm hexhole in it. Hold the bolt with a 22mm boxend and turn the center hexhole to remove. You can buy a set of hex driver sockets for under $10.00.
Removing the strut is not difficult. Look at the washers and spacers needed and use them all. Installation of the new strut was difficult only in aligning the holes for the bolts.
Remove the jackstand and replace the shock on the other side. I timed this just right so as to work in the shade. I wish I could keep a hat on doing this, as the top of my head sunburns easily.
The rear shocks involve emptying most of the stuff in your trunk, because you will have to pull back the trunkliner: it is springy and has no fasteners. It is basically a wrestling match between you and your trunkliner. pull it out starting from the back, then the top. Be as gentle as you can, but firm enough so it knows that you are Herr Bossman, ja?
Jack up the rear and slide in a jackstand. Remove the wheel, then the two 10mm retaining screws on either side at the rear of the plastic access cover. Then pry the access cover off, it is mostly a spring fit affair: you could use a small standard screwdriver or a very strong fingernail. I prefer the screwdriver myself.
Squirt WD 40 on the nut of the transverse bolt that runs through the bottom eye of the rear shock, and on the two nuts (a nut and locknut combination) inside the trunk. Then remove first the one on the bottom and the then the locknut at the top. Note when you turn the second nut the entire shock is also turning, so you will have to hold the top of the shock still with a 7mm openend wrench or a baby visegrip carefully applied so as to hold it in place.
Removing the shock is not easy, because you have to pry it up and over and out of the cozy little nest in which it sits. I used a 22mm openend wrench, assisted by a 1 foot prybar. I was gentle, but firm, ja?
It is fairly simple to stick the shock into its hole. Once more, kindly Herr Bilstein has provided new rubber thingies. Push the largest rubber donut on top of the shock, stick the top of the shock into its hole, and place the smaller donut (writing side up) and the large fender washer on the shock inside the trunk. Lacking a torque wrench, I screwed it down to the same number of threads remaining as it had previously. This takes some muscle, as you are squishing two mighty Teutonic rubber donuts. No time for slacker girly-girls here!
You must then manoever the base of the shock up and over into its nest, so the holes in the eye of the shock line up. I used a jack, but if you are really strong, perhaps you could compress it with your mighty arm (invite Arnie Schwartenegger over, maybe: serve knockwurst and ust enough Pilsener lager). Stick the bolt through it and tighten it down and do the other side. Remove the jackstand and you are done, except for deciding how much of the clutter in your trunk is really necessary.
The HD shocks and struts are externally identical in every way except the number to the original shocks. You will not need to replace the springs, but if you do, get a two-piece strut compressor, the one sold by Harbor Freight appears to be unusable on 300D springs because it is too large.
I deemed this job necessary due to the ripply cupping of my tire treads on the front, which dismayed me. I decided to replace the rear shocks for sport. I notice that the car has much less sway in a turn. and no nosediving a la 1982 Buick Regal is even a panic stop.
As a lad in Missouri I once put wheels on Falcons and Comets at the Claycomo assembly plant, and with a friend restored a 1948 MG TC and a 1950 Jaguar XK120 coupe I wish I still had. Not so much because they were all that much fun to drive, but because they would have been quite valuable by now. We shamelessly painted both British Racing Green (even though Jags dod not come in that color that year), and put on go-faster stripes, and sold them at a nice profit, considering the minimum wage in 1959 was 75 cents an hour, and working on cars was more fun that mowing grass. When we got tired, we shot rats with a bb gun in the barn we borrowed to work in.
The Mercedes is easier to install shocks on than my unlamented 1982 Buick Regal. I am rather sore all over, because teacing Spanish does not involve the same sort of contortions and rolling about cussing on the patio. My neighbors and NPR provided accompaniment.
I am very happy with the results and thank this forum for being so useful in telling me most of what is involved in replacing the shocks and struts.
300D 2.5 L turbo, 138,000 miles