Check the usual things like brakes, tyres, suspension etc.
Also check for leaks from the injector pump as this is common with some of this new low-sulphur diesel that is being sold these days.
Almost ever late model Jap import vehicle is auto. Manuals do exist but they are rare and **** hard to find. The japs love their autos. You would too if you spent most of the day sitting stationery in traffic or crawling from one set of lights to the next.
As for the air-con - it SHOULD have it. Every jap import Hiace I have seen has air-con fitted as standard. What I do find though is that some people remove the belt from the compressor on the basis that they think it is dragging power from the engine all the time. This is in fact not true. The compressor only uses power when it's activated - when it's not, an electro-magnetic clutch disengages the drive from the engine, so all the belt is doing is driving a pulley.
The other time people seem to remove the belt is when the system is low or empty of gas - so that could be an issue as well - if it is like this, it could indicate a leak somewhere.
Check the dash near the heater controls for a button marked 'A/C' - then lift the engine compartment cover and check to see if there is a compressor located near the driver's side of the engine at the top.
Here's a photo of one:
http://www.2carpros.com/images/ac_compressor_clutch.jpgAs for some kind of 'external' unit, I've not heard of such a thing before. At least not on a Hiace.