Our previous van was 1.8T and did benefit from being manually changed down when climbing or descending hills. Our new van is 2.5T and I'd much rather do it to reduce engine strain - so that's not only manually changing down, but keeping the engine speed up near the torque converter's stall speed to minimise losses there (stall speed is between 2700 and 3100 rpm which is a little too high since we develop max torque at 2,000rpm).
I won't go into the safety gear but I will add that a good proportional brake controller is very important. I had a Redarc in my Commodore and didn't like it, it was never proportional. I had a Tekonsha Voyager fitted when I bought the Navara and it did ok but didn't like hills - up or down. Every time you changed the amount of slope you had to set the thing up again. My Tekonsha Prodigy P3 does it all for me.
Putting on a set of Clearview mirrors will also help, if you can afford it ($800 or so for the pair). Big, big mirrors and you just pop them out when you're towing and push 'em back in when you're not.
Here's a look at the rig, still looks the same today (from the front). Will get a solar panel this weekend, finished the rewiring of the panel tonight and will buy the fittings to mount it tomorrow.
Other than that there's not much to add. You'll discover things you might like to do that others have done. Here's one: the van in the above pic has a 3-way fridge, my previous van (shown in my current sig below) had an all-electric fridge.
With the previous van I had an inverter that produced enough 240V to drive the fridge (which auto-switched to 240V if that was available) and ran a C-Tek charger to keep the battery topped up. I'd send 12V to the caravan through the 12-pin plug, then pick that up inside the van and feed it first to a relay, which closed and changed the input power to a double-power point from the van's 240V system to the inverter's output. The 12V then supplied power to the inverter. This allowed the fridge to disconnect from the battery and gave the charger a perfect view of the charging state of the battery (plus the battery could charge faster).
In the current van it's even more important. 3-way fridges have (oddly enough) 3 methods of providing its power. It's all the same - heat - but only the gas and 240V options use the thermostat. The 12V alternative uses slightly less watts but doesn't use the thermostat. If you open and close the fridge while it's on 12V, it really struggles to recover especially on a summer's day in the outback! This gremlin is defeated by inverting the input power to the fridge and plugging the fridge's 240V in to the inverter. Now, it takes about an hour of driving for the fridge to reach "food safe" temps (2 to 5 degrees celcius, we like to keep ours at 2 to 3C).
Hope that helps!