Here is what the entire OE kit looks like:
You can see the 7 to 4 pin adapter plug thing right above the towing module. Looks like a big key thing. There appear to be plenty of aftermarket harnesses for land rovers, VW, that go from Euro to 4 pin so that's an option if the pinouts are standard on the Euro plugs across marques.
To visually check for the towing module you'd have to go under the spare tire/compressor to look in the electronics tray. I haven't used INPA or other software to query it. Wonder if the NT520 can do that?
As for the receiver/ball setups I don't have an answer. I haven't look into it yet as I have not needed to tow with the truck yet. I'm sure I will frantically search for these things when the need arises rather than being proactive and getting them ahead of time.