My understanding of Garmin's Topo Australia is that it does indeed autoroute, which is what you are after. Saving a route as a track shouldn't be hard, I know I've done it in Mapsource but I can't remember how or why I did it.
The GPSMAP60CSx is a damn fine GPS too, with one caveat for the use you intend.
It will recalculate a route EVERY time you load it up, regardless of any other setting you may use. it may send you places you didn't want to go. It is a "feature" of these particular units, discussed at some length in the main gps forum here, and the workaround to get it to do what you want it to is quite simple.
Hope this is of some assistance.