I'd land & stay at the Asses Ears Wilderness lodge in the Grampians. You'll give away a star or two in accommodation, but gain it in the experience.
Welcome....
I'm not sure I'd bother with Broken Hill, but maybe consider Tiboburra.
If you want a bit of luxury - Mildura & the Grand Hotel. Be sure to book Stefao's restaurant in advance.
I'm not sure I'd choose to stay at Portland. Maybe Hamilton or Warrnambool instead.
In Melbourne, I'd pay the landing fee & do Essendon for the city view and general closeness to the city.
If you have time, you could consider an overnight trip to King Is or Flinders Is from Melbourne.
Lakes Entrance to Albury is over some tough, remote terrain. I wouldn't do that. I'd skip Wagga and go Lakes Entrance to Merimbula to Canberra.
Make sure you have you ASIC card & Aussie licence sorted out at least 3 months prior. You also need to consider fuel planning. Where you can get fuel and how best to pay for it (cash / credit card / fuel company carnet). Make sure you carry water an EPIRB and a basic survival kit. You should probably also buy AVPLAN or OZRUNWAYS for your iPad.