Agreed with most from this post, one question...auto or manual?
We have Navara's at work, drove one on and off, not bad.
You said that it has towed a 14ft van around Oz, so it has done some work, a 14ft van about 1000kg to 1500kg depending on options of the van and what was loaded in the Navara. That being so, get 4x4 specialist mechanic to check the clutch, gearbox and associated drivetrain.
The mechanic you will need for the inspection would be a 4x4 specialist, not a car mechanic...an experienced 4 x 4 bloke who knows the ropes.
Then go by their report on the vehicle and haggle away....but don't fall in love with the thing, its got some bells and whilstles, looks nice, but it is still a 4x4 with ks on the clock and there are others around in the market place as well.
Good luck.