I think that Benzmac proposed the correct solution.
The reason I asked the question was purely a cost vs return issue. If you do your own work, I was going to encourage you to dilligently work through your problems, and get it up in shape. You would be able to justify this, because it would be economically feasible.
Since you take it to a shop, and since you live in CA. I doubt that Donnie or Steve do your work. If you have a competent shop that you know and trust, determine what it's going to cost to get everything done, and then determine whether it's worth it or not. If you don't have that shop, find it.
There a lot of MB's in good shape as long as you're not in rust country. If it's going to cost a fortune to get your car the way you want it, find a solid car that you can keep up, instead of chasing to catch up. Then find a shop in your area with someone like Steve or Donnie to consult and do your work.
At that point, if the least little thing is broken or needs adjustment, go get it done as soon as possible. By taking this approach, you will keep from letting the car run down to the same point, which causes the same emotions and puzzlement you feel now.
'84 Euro 240D, 516K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in