as everyone has said ,basic service parts are available at whatever spare parts place you use
Dave at USGM serviceparts(pontiworld ) has a large selection of whatever else you may think you need either pick parts up from Oak Flats (just south of Wollongong ) or receive via freight in a day or so .suggest if its a corier delivery check the package for damage BEFORE signing for it (most important now days )
as far as mechanics .the cars are not overly complicated IF you have a decent mechanic now he will not have any issues learning the subtle differences between USA and Aussie cars
the main bug bear with these cars is the tune port injection .....for some strange reason many mechanics do not have a clue YET its in reality a simple system (particularly the 91-92 models ) as they are a MAP based system similar to the commodore (NO NOT THE SAME ) IF you understand electronics there are also some programs that you can run on a laptop and connect the ecu direct to your laptop to read in real time what your engine is doing