Local hobby shops have plenty to offer regarding N Scale models of American and British trains. In the past, there has been very little in way of Australian trains in N Scale but there have been a few models appearing in shops in the last year or two and more on the way. Unfortunately, due to the smaller world-wide market for Auatralian models (N or HO scale), production runs are smaller and therefore costs are higher. In the past, nearly all Australian models were scratch built by experienced modellers or foreign models repainted in local liveries. Fortunately, these days there is a growing range of Ready-To-Run models and a growing range of models in kit form, requiring assembly, painting and detailing.
Australian N Scale locomotives use "close enough" equivalents in foreign locomotives for their driving mechanism, with the outer shell replaced with polyurethane or brass models of local trains. The donor locomotives are usually American models, Britain uses 1/148 instead of 1/160 for their N Scale so these are a little bigger than we would like. The mechanisms sometimes need a little alteration to suit local prototypes or to fit into the local model shells. There have been some thoughts of building mechanisms using off-the-shelf spare parts and some custom made components for models not having a readily available alternative.
The brass models come in kit form and require soldering parts together, before painting and detailing. The polyurethane model kits are easier to assemble with generally just a few parts to put together, and then similarly painted and detailed. Some models are easier than others and some liveries easier than others. Some are certainly possible for novices like me and some I have no desire to attempt at this stage.
The easier option, of course is to have someone else do the work for you. Aust-N-Rail and Powerline have released several Ready-To-Run models in recent times (some shown on this website) and Frate-N sells a range of kits completed for you, though mostly NSW trains. Have a look at "Where to Start - Rolling Stock" and the various models shown on this website for examples of what is available.
Aust-N-Rail has released several excellent Ready-To-Run models fully designed by Aust-N-Rail and manufactured in China. Numerous models are available in kit form from a variety of manufacturers. Skill levels required vary but many are simple enough even for Klutzes like me. Websites for the main manufacturers of Victorian models are listed on the "Links" page of this web site. Frate-N sells a range of completed kits.
The range of passenger cars available is smaller, though the recent release of E and W type cars by Spirit Design has boosted this. I'll have a few ready to post on this website in the not too distant future. The Z type cars from Aust-N-Rail are simpler to do. Rumour has it that more passenger car models are on the way.