Yes it is a DIYer and Bilsteins are the shocks to go with. Mercedes has been using Bilsteins forever, well 40 years at least. I am sure the procedure is the same for your chassis as it is for mine, W116. First, remove the back seat. This will allow you access to the top mounting bolt. Second, raise the car so that the trailing "A" arm is at it's lowest point. Put some jackstands in place, freeing up the jack. Remove the 2 lower bolts that hold the shock in place, I believe they are 17mm. With these bolts removed the shock will drop. If there isn't enough clearence to pull the shock out through the A arm, place the jack under the A arm, out towards the wheel. SLOWLY raise the A arm until there is enough room to pull the shock out. Installation is in the reverse, with one important safety tip. When you go to tighten the top bolt, hold the rod in place so that it doesn't turn. I used Vise Grips for this.
Hope this helps.

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member