Circling back around to this thread, I never did anything with the MDX's radiator. And, fortunately, the cooler fittings haven't gone south yet. But I feel that the longer I go, the longer I press my luck on what is a fairly widespread and documented problem (ATF cooler fittings failing, allowing the coolant and ATF to mix inside the radiator). The fittings on ours have some visible corrosion on the outside, but it's not too bad. The problem, here, is there is sometimes internal corrosion that hasn't yet made it to the outside. If you see corrosion on the outside, the advice is to change it, as there's probably corrosion on the inside as well. So I feel that I'm overdue on this.
Many Pilot/MDX/Ridgeline owners have found generally good success with Spectra Premium radiators. I can order these online from Amazon or eBay for about $100-120 delivered, but there are also numerous reports of damage in shipping (boxes damaged leading to fin damage, etc), so I prefer to buy locally for this. I got a 30% off promo code in my email this morning from Pep Boys, and that prompted me to actually buy one. Pep Boys sells the Spectra Premium brand, and the model for our MDX (CU 2740) is $199. With 30% off, my out the door price with tax is about $145, which is pretty reasonable. It should be to my local store on Thursday. I will inspect it for damage at the store before I take it home. Assuming it's not damaged, I plan to install that this weekend.
I will document with pictures and post a thread and link that here to close the loop on this.