Honda claim the transmission oil doesn't need to be changed unless you use the passport under severe conditions. There is a drain plug and a smaller fill plug on the underside of the transmission. Pump Dexron3 fluid up into the fill plug until fluid spills out the fill plug. Honda want the transmission checked with a scan tool with the oil at 100 to 150 degrees F.
I love technology and a lot of what is being done with modern cars to make them more reliable, but more and more manufacturers are shutting owners out of doing any thing to their cars except put gas in them. The transmission oil is topped up using the "overflow plug" from under the truck. The oil temperature has to be at a certain temperature (and it is critical) before topping up the fluid.The logic is if its leaking it needs to be removed and have the leaks fixed.