When I did the dis-assembly I didn't actually hitch up the the hitch in the truck, but I did use the truck and the trailer jacks as you suggest to take the weight of the pin box. I don't think hitching it up would work. I think it would pivot on the hitch. They say it can be done with two people, but I didn't have two strong people handy so I had to use something else!
I put a few blocks of wood on the tailgate (when it was down) and then lowered the landing gear of the trailer until the pin box was almost touching the wood blocks. Then I wrestled with the pin box until I persuaded it to come loose. Then I raised the trailer and pulled the truck ahead a bit to get at the pin box, now in the truck.
Going together wasn't too hard but you need to make sure the pin box is going onto the shaft of the trailer straight. Don't rush, and wiggle it around and it should slip on easily. Just use the trailer landing gear to slid the trailer into in. Then put the big nut on and pull the truck out of the way.
Before I did it I'd read somewhere that I should not lube the shaft the nut attaches to... then, after I was done, I read the instructions a bit closer and see it says:
"use lithium on the wear plate, wear bushing and bearing."
The wear plate is the piece of plastic stuff (not sure what it is) at the top of the assembly. The wear bushing is a piece of the same material on the bottom just above the big nut and washer and, I assume, the bearing is the 'hole' the shaft goes through. So I guess I should have put lube in there as well. Humm, read instructions first!!
I this I got enough lube in there anyway, but I'll be sure to lube it when I do this next year.