Yeah, it looks easy to do in theory. I just think the running of wires through firewalls etc could be a pain. Also I can't get another tray in the engine bay of the Navara so it will go inside the rear tub on top of the wheel arch, quite common in some twin cabs apparently.
Have a look at thumpers or arkpaks, easy to install & transferable between vehicles.
You can make your own far more cheaply if you have the time, desire, skill.
The procedure is available on most 4wd forums.
Oh, & I love my camping, 4wdriving, fishing.
Ive had a couple of Landys but, my current 4wd is a BT50.
Its worked out of every day & then reverts to a recreational vehicle as required.
Its got all the gear to tour the vic high country.
Its an extra cab with a 7' work & play f/glass canopy that sure beats sleeping in a tent when its raining hard.
Its also great at pulling the van.
Let me know when you want to go wheeling !!!!
ps, my 2nd batt is mounted on the chassis.