Luke,
mine is for sure the heat exchanger itself is leaking. I see no coolant in the connectors or hose.

My concern is taking the oil inlet/oulet from the heat exchanger in the process of replacing the exchanger. Not sure if special tool is required, hope Weasel can chime in, right now I can drive my car but if I mess with the oil lines and it leaks than I am screwed (I'll be loosing auto trans oil).