The early 2010 STs had turbo actuator problems, but haven't heard much about the later models - they might have fixed the issue.
I think the timing chain issue is a bit of a scare, I'm not sure that a properly-serviced and not overly-punished vehicle is going to have a lot of problems in that area.
I'm assuming you're talking a diesel. They do get a little thirsty with big loads, my 1.8T van generally uses 17-18LPHK which isn't too bad given it's a full height caravan and we prefer mountainous areas.
Nissan are not allowed to neglect the warranty if you service the vehicle elsewhere, although they will happily try to blame someone else for the problem - then again, what vehicle manufacturer wouldn't look for an easy out? They have to watch where they're spending and putting the onus on someone else is a cheap first attempt for them.
The other areas that would concern you, towing - the D40 Navara is a very comfortable vehicle to travel long distances in. Mine hauls our caravan nicely, through mountains, desert, forest trails, little back roads or freeways with ease. Sure it slows on the hills, but that's because I let it slow down - I don't believe in flogging it.
There are a couple of things you could do to the vehicle before a big trip, too. First is an EGR mod - just replace the gasket near the EGR valve with a piece of stainless steel (and use Permatex Ultra Blue sensor-safe gasket cement on both sides). If you cut it like the gasket, you'd hardly notice it during a vehicle inspection.
Also, consider fitting a catch can - these things pump oil out the PCV a lot more than petrol engines.
Apart from the other mods that you could get - driving lights, a snorkel, good window tinting and a decent in-dash GPS system would be my recommendations. If you're doing a lot of outback/bush (including coastal roads with sparse population) then to protect the vehicle from roos, emus and boars, you might consider a full steel bullbar. Fit some roo whistles (about $5 at auto stores) to the front of the bar.
At the rear, Hayman Reese make the hitch for Nissan and it looks like Nissan now use the multi-point mounting, so a load leveler (essential for the weight you're hauling) is going to be fine - just make sure that you ask for one with vertical and horizontal mounts and don't get old stock.
You probably already know about proportional brake controllers, but if you don't, we use a Tekonsha Voyager, but the Prodigy is a step up and you might consider that. Either works very adequately, but just make sure they use 6mm cable from front to rear, as the smaller cable gets warm under extended braking.
I think I've covered enough!
