Ummmmmmmm, done a couple of those this year......
Due to the weight, etc, I would recommend that you fit the gearbox first and then the transfer box.
You'll have to jack the gearbox/engine down to make it easier to locate the transfer box.
Assuming you are not doing it in a fully kitted workshop, its going to take at least three-days and you'll need three people to get the boxes into position.
Chris
Note: make sure you spray all nuts/bolts over a few days before doing and make sure you have some spare N&B's..... :idea: