you need to replace all of the all of them or they will all leak over time i think there are 12 dont go to mercedes they will charge you $5k. There are many private shops that can do it. I just had my 2001 sl 500 done for $1000.
Very easy to replace seals on hydrolic actuator. There are several videos on you tube that will show you step by step instructions. I have already did 6 of them. Takes about an hour and costs about 50$ for kit at mbseals.com. Good luck!
Call "TOPHYDRAULICS.COM and talk to them before you spend a Dime. They have video and instructions posted on DIY removal and installation of cylinders and you can also find valuable info videos on YouTube. Once they are rebuilt a good mechanic can reinstall for way less than a dealer if you don't want to do it yourself. Either way, it's cheaper than going to the dealer who will start calculating charges before your wheels clear his driveway.