I have a 1986 420SEL, that has an oil leak that appears to be coming from the rear of the engine and in front of the transmission.
I am on the verge of taking mine to Mercedes to replace the rear engine seal too. When mine drips, I notice it in the level of the oil stick.
I was able to get it up on a lift to examine it up close but could still not determine where it was dripping. What did they tell you when you had your seals done and how much did it cost you? Did they have to remove the transmission to get to the engine seal?