You've made a remarkable set of discoveries:
1. You may have accidently found one a few trustworthy MB mechanics that knows these diesels.
2. You should now know how to shut the engine off with the stop lever if the vacuum fails.
3. You've found a good source for information.
4. I'm in Denton, just north of DFW airport.

Charles

PS: Did the mechanic assure you that the leak in the brake booster would not be a safety issue?