The suspension of the W210 (both front and rear) uses a series of rubber bushings. These are wear items and have to be replaced periodically. There are DIY guides several places including the site mentioned.
If by struts, he meant shocks then the front ones are pretty straight forward. The rear uses a hydraulic system and is more complicated. Usually, the accumulators at the rear fail not the shocks themselves. I think rear shocks are going for about $500 ea. So if they're needed the bill might be reasonable.
If it were me, I would start with the bushings and see how much things improve. I think you'll be surprised.
