I have found the
www.airshow.net.au to be totally useless in the lack of information on how to get there.
http://www.skybus.com.au/info-time.htm will get you from the Airport to Spencer Street. which should take about 20minutes.
http://www.vlinepassenger.com.au/tim...vline_glng.htm
It is 48minutes from Melbourne to Lara Station.
Hope that helps, that took me about 20 minutes to find out all that out when the airshow web site could have provided.