I have reread your post looking for whether you are looking for manual or electric shift, still don't know.
Manual is easier to check, IMHO, move the shift lever up and down while rotating the input shaft and put your shift hand on the case while still turning the input and feel for roughness. The shift will be distinct with a loud click as it moves into low range.
For both styles of cases, remove the fill plug, check the color of the oil, (generally it will be automatic transmission fluid red, I have seen it in green) either way, it shouldn't be dark or smell burnt. While you have the plug out, poke your finger into the case and feel for the chain, your should be able to put your finger under the chain and try to lift it, (you will want to turn the input shaft reverse of the direction you have been turning it to unload the chain). Replace the plug. Plug of the vent hose. Turn the case upside down and repeat the process with the drain plug, some drain plugs will have a magnet, check it when you first remove it.
Take your time, while you have it upside down, check the tag for information, especially the numbers, 1350 or 1354, if it is 1350, pass on it. You won't find a lot of 1350's with a yoke/flange on the front out put, but they are out there and you don't want one.
Electric shifts, I haven't found a way of shifting without having it in the rig, (I'm sure others have) but you can still do the other checks.
The tighter the chain, the better the odds of a good part, the cleaner and brighter the fluid color the better. If it feels rough when you turn the input in, pass on it.
The chances are in your favor of finding a good case, most were used for highway use only and then only when the conditions warranted the use of 4 wheel drive.
I drove 80 miles on Tuesday to pick up a 1354m, I know what you are saying.
Good luck and have a safe trip.