First things first. Is the contamination in the coolant reservoir oil (light brown?) or transmission fluid (red?). Drip some on a piece of white paper if you can't tell by looking. It's hard to believe it's a head gasket if there's no coolant in the oil. Cooler leak would also have coolant in the transmission.
Is it possible you or someone accidentally contaminated the coolant? Has the engine been overheated recently?
I would drain the coolant (including the reservoir), change the engine oil, and flush the transmission fluid. Keep them for inspection - don't dump them into a drain pan to be contaminated by old oil or whatever. Eventually, you will see the problem in the used fluids. Keep a close eye on the new oil and transmission fluid.
Forget the Bars leak.