Minh,
You don't have to buy all the documents Seagull listed. They are all online and free.
You will have to do the Class 1 medical again but that shouldn't be too much of a problem. Will take some time though. I can't see why you would need the CAAV to verify your hours as you are not converting your Vietnamese licence.
You will do as much training as the instructor deems necessary for the checkride. An ILS with a RNAV will be sufficient for the test.
I have heard good things about a training school in Shepparton too.