Many insightful observations. Thank you.

In considering the "money pit" question, I think it's important to keep the alternatives in mind. Compared to a new car and the insurance, taxes and registration costs that go with it, a well-maintained W123 is probably not a money pit. Compared to any other similarly priced used car, my guess is that a well-maintained W123 is going to have similar bills, regardless of whether you do your own work or have a mechanic do it.

But because I'm returning to the classic MB world after a long absence (just bought a well-maintained '85 300D for $6500), I could be totally wrong. I'm very curious to know what the veterans here think.