Take a look WAAYYY back in the threads. You'll see one in particular where I pissed off the entire North America Mercedes-Benz community with concerns similiar to yours (I called Merc-Benz's junk).
I'd just bought a 89 190E 2.6 and replace the same items you did, save for the water pump. I was upset when things kept breaking. It was a money pit!
But, I kept fixing problems, one by one...
Now... I would never buy another car but a Mercedes. Currently I'm shopping for a new C Class for my wife.
My advice is hang in there and be patient.
About the trans., let it warm up longer, AND check you trans. fuild. It may need changing. I had the same problem, and it was due to low trans fuild.