Take overalls and a torch because the first place you want to go is underneath.
General chassis corrosion...see Border20's current thread for couple of pics showing just how bad they can get.
Check the inner sills between sidesteps and chassis especially at both ends, these get heavy weathering and can perforate if left.
You don't say what model, but check everything works including the aircon, very regular that the pipes to the rear aircon unit leak.
Ideally all 4x4's with permanent all wheel drive want a set of tyres with similar tread depths, or the centre diff will be working constantly to adjust.
As with any car look for leaks, check the coolant is nice and clean and preferably red, cehck the engine oil and brake and power steering fluids, obviously you'll be looking for some sort of believeable service history that matches the MOT history you will already have checked.
Brakes should be light and very powerful showing no signs of pulling to one side.
I don't know what experience you have of Landcruisers, but don't be afraid to walk away even if you feel under pressure due to your travel arrangements, most of us have travelled many miles to look at LC's and winin minutes of sliding underneath have been back in our cars on the way home again, my record is probably 3 minutes of inspection, only looked underneath never opened the doors or bonnet, it might be the case you check half a dozen or more before you find one in good enough condition underneath to be worth buying.
As TONYCY11, its not usual for Diesel injectors to be cleaned on these, maybe the seals where changed recently but you can only surmise whether the oil pick up was inspected or for what reason were the injectors cleaned and whether there might have been oil pressure loss if the oil strainer was blocking up...no oil pressure gauge on a 120 and pressure would be very low to trigger oil light.
Try and start it from cold, oil light should go out in a split second, there will be condensation from the exhaust but 120's do not smoke, nor should there be any smoke even under full power acceleration.
It might sound a bit rattley on cold start but this should quieten down and by the time the test drive is over there should be no rattles at all.
You will know how much road salt its seen by the wheels, the facings should be diamond cut and laquered and the non facing painted silver, if they've been refurbed then chances are they are now all painted without the diamond cut and laquering, painting is cheap, refacing and refurbing our wheel properly is going to be over £100 a wheel.
As a guide, mine is 2005 and covered 111k miles, the wheels are still original but spiders webs have started and i've had to touch the wheels up in several places with laquer but still look pretty good for 15 years.
As with any car, judge the vehicle on its merits, if its a private sale judge the owner, don't take too much notice of any dealer spiel if its at a dealership.