The end by the wheel failed - the exposed shaft just broke off inside the boot and fell out. I am not sure what caused it, but my local mechanic has indicated this is not rare - not a daily event but he has seen it a few times. I have not been able to get there to see it, as I will be doing the work with my son next weekend. I will try to take some photos and show them once the job is underway.
The new half-shaft from Partsshop was $285. Shipping was free. I will try the sources you suggested. I went to the Snap-On Tools website and they have items going by the name of triple square and double hex, and they do not list M10 and M12 as sizes. They only show 10mm units and smaller. We have a Snap-On guy in town and I will chase him down tomorrow I think.
I have looked the procedure over on the CD. It suggests the rear wheel bearing is captured between the rear axle shaft flange (at the bearing inside diameter), which has the splined interface with the half-shaft and bolt circle to attach the wheel, and the wheel carrier (outside diameter of the bearing). To get the wheel bearing out you have to remove the half-shaft and then somehow pull the rear axle shaft flange out. At that point you can pull the bearing out of the wheel carrier.
I will try to get some photos of the procedure if it is practical. Lying on the ground with the car on ramps or jackstands will not make taking pictures all that interesting.
Thanks for the sources. 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)