Given my driving style and climate, it seemed an oil cooler would be prudent for oil/engine longevity, as my motor has relatively low miles on it to-date. Using stock BMW parts gave me two options. Oil to air, or oil to coolant.
The oil to coolant (flat plate exchanger) option seems better suited to stabilizing oil temps given my climate and driving style...especially because it can also warm the oil after cold starts. (I see that oil temps lag significantly behind water during warm up.) For high performance driving, I would've gone with air-oil. The N52s installed in larger vehicles (and in other countries) had the air-coolant option.
Finding parts was easy...but not well documented on the internet.
This link details the oil filter housing with cooler assembly.
This link details the hose connections for the cooler assembly.
Because my car is a manual, I needed the coolant pipe (11537516414) because mine did not have the hose barb for external heat exchanger(s). If you have an automatic, you'll already have this. Just replace the hose running to your trans cooler to the one that supplies.
The coolant pipe was $16 on ebay. The filter housing and exchanger assembly was $65 on ebay. The hose was $17 on Amazon (Rein CHH0507.) New gaskets for the housing and exchanger were $11 each.
The hose support clips on the front of the engine (two) were already present to support the added hose.
The hardest part of the job was getting the screws back into the new coolant pipe. They're small, and even with the front exhaust manifold free, there's barely room to get your hand to the screws. Wobble extensions were critical for me, and it took me four tries repositioning the hose on the end of the pipe to get the screw holes to line up perfectly. If you have an auto trans, you won't need to bother with this. For me, total time was about 4 hours.
For the record, you don't need to remove the intake to get to the filter housing bolt that is under the first runner. I used a long 1/4" extension, a 1/4" flex adapter, and the correct e-torx socket (on a 1/4" to 3/8" adapter) to make it happen. Amazon has some flex extensions that I may add to my kit for jobs like this.
Worth it? Maybe. I needed to do a coolant flush anyhow. Oil temp comes up faster and tracks right with coolant, and that was the point.