Doin Time
CASA is transitioning into the CASR's (Civil Aviation Safety Regulations) which will replace/incorporate the Civil Aviation Regulations.
If you have 100 hours night experience you are able to attempt the flight test straight away. Aus requires 10 hours dual night instruction before attaempting a flight test for the granting of a Night VFR rating. If you have already done this in the US (I would assume you have), you meet the requirements. There may even be a chance that CASA may recognise your US night VFR rating and issue you one on your Aus licence.
A couple of other differences between the US and Aus system is that type ratings require a minimum number of dual instructional hours before being "qualified" on that aircraft type. This is not a rating and does not need a flight test. It is up to the instructor to deem you qualified.
Look at
http://www.casa.gov.au/rules/orders/040.htm for the requirements for all ratings and aircraft endorsements.
Hope it helps.