I just finished replacing all 11 actuators on my '99 sl500. Not too bad of a job, just took a long time to figure out how to get to all of them. I was on the Mercedes list and was given information about tophydraulicsinc.com in OR. They have a great DIY section that show how to get to everything and also rebuild the cylinders. I was extremely happy with their very quick service and excellent product. They are very reasonably priced. I had a few problems and sent emails for assistance and got almost instant replies. No financial interest but highly recommend them if you have hydraulic problems. I found that at least 4 cylinders were leaking although there was so much fluid in some places it was hard to tell which were bad.
Pete