When the head gasket leaks, it is usually only an external oil leak, this problem has not been known to mix coolant and oil. To the best of my knowledge, the problem has not been fixed for the 97 engines, but someone correct my if I am wrong.
As far as the tranny goes, if it behaves like it is supposed to, then do not bother with the computer or valve body. My C280 has not had either changed and it is just fine.
On my mom's E320, they changed the computer. There was a vibration from the driveline in the 35-45 mph range. Although the dealer never said why, I attribute it to the torque converter clutch fully engaging with near zero rpm slip at lower speeds instead of following its program of computer controlled slip at that speed range and thus transmitting vibrations through the drivetrain. It was no major problem with her car, but it was not behaving like it was supposed to, was covered under warranty and would not have made a major difference if it was not changed.
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record