I noticed this morning there was oil in the coolant reservoir. A repair shop said it was the auxiliary engine oil cooler that went bad. Does this sound right? If so, how hard is it to replace? Thanks!

 

There needs to be reasonable assurance it is the cooler coil first.
Is the oil deposits reddish or blackish?
The coil is put in the end cap and sealed with fittings before is it put on the core.
Either replace the radiator or disconnect and use an Aux cooler.
The difference will be from a cold start the trans will take somewhat longer to heat up before allowing OD to function until the fluid temperature reaches about 98 degrees.
Good luck.

 

I guess the oil would be more red than black.

 

did you ever get a conclusion on this subject? Im having the same issue. mine is the 5.4 2v

 

I never have. I am getting a new engine oil cooler this week. I'm going to put it in, flush the engine and cross my fingers.

 

what is in the coolant ? Motor oil or transmission fluid ? If it is motor oil and it is from the coil in the radiator, just bypass the cooler as mentioned and prove your theory.