Hi Danielle,
1.If you book your airtickets from travel agents, they'll get your visa for you..
2.If you don't mind backpackers, you can try out YHA, they have ensuite rooms, the place is clean and comfortable (just came back from a roadtrip to syd and canberra and stayed at YHA), you can check them out online
3.starbus is direct to most hotels but it's slightly more ex (an not 24 hours), $17 per trip to certain parts of the city. for skybus you need to go to spencer st station to change to the hotel transfer bus..
4.cars are approx $39/day on average, petrol this few days is $1.20-$1.35.. so far we've used Europcar, Budget and Metrocars.. Europcar is the most professional (according to SO, i'm just the passenger)
and for GOR, may be better to take a day tour, cos the drive is not easy if you've nv driven on those winding roads.. it's really by a cliff and just single lane up and single lane down.. if you drive slowly, you will feel really pressurized..
You guys don't wanta visit Philip Island, Yarra Valley, Grampains or Mt Buller?