Oil leaking bad at the oil cooler

[NHBaler]

I noticed a bad oil leak on the driver's side of the engine after we had some below freezing weather looks like it is coming from the oil cooler I guess that is what that tube is on the left side of the engine, What is the next step to take it off and repair it? Can it be fixed with new o-rings and gaskets or something? Is it hard to get out? I forgot to say this is a '84 6.9
Thanks

 

[HammerDown]

I feel your pain...getting my Pop Corn out for this one.