If you did not keep running the car and the boil over event was kind of "after the fact" meaning the water boiled away to cool an engine just sitting there, you are probably ok. As the water in an open system reaches 212 degrees Fahrenheit, it boils and the phase change takes a lot of energy with it. If you did not run out of water, or run it down to the point where it was not boiling in the head area, you are probably ok. As noted above, the head is pretty stout, and if the event was a boil over only (not run dry) you probably did not reach excessive temperatures.
My daughter just did this to the 1982 240D in our household and she called me to tell me the gage was in the red. She noticed it after God knows how long. I had her fill it with the anti-freeze mixture in the trunk (always carry a 50/50 mix in a gallon jug in an old car) and go buy some more. We diagnosed a leaking water pump and she took it to a local mechanic in Schenectady, NY who fixed it the next day. No damage to the engine.
Good luck, 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)