well most of your mechanical parts and things are readily available in australia, AE82 Twincam and the AW11 MR2's have basically exactly the same motor (i think in fact the only difference is the ECU), and much of the suspension components will be the same as the australian delivered models.
brakes im not sure about.. i know rotors/calipers and stuff are pretty easy to find but you're not going to need them anyway
panels are the same as the ADM models, lights are gunna cost a bit for the actual units (whether it be whiteline tail lights or even just the JDM headlight units) but i dont see why you'd need them either
as far as reliablility and day to day driving goes, 250K's is probly the upper end of the scale for an import, but its a toyota not a datsun so it'll be fine.
also technology isnt the devil.. airbags save more lives than they take, and failure is pretty uncommon.. things like vvti and stuff.. its all good