The most obvious sign of worn springs is the ride height of the car empty and loaded.
With new shocks the car ride height should meet the specs in the manual, measured unloaded and loaded.
If you drove with shocks that were out of oil and the wheels were banging into the stops for a while, I would find a dealer or MB independent shop with good credentials and have them check it out. If the spring, out of the car is not up to its design free length, it should be replaced, or you can add a spacer to make up the difference in some conditions. I am not familiar with the typical kinds of measurements made on auto springs but would suspect a check of load capacity per inch of compression should be part of the check. This would be more important if the spring free length is ok and the rear of the car sags, or if you use a spacer on a spring with a known short free length.
Hope this helps, Jim
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)