Go onto the
www.australianopen.com website for tickets. Or you can get them at the gate. It depends how much you want to spend and what games you want to see. The major stadium is ticketed seated tickets varying in price. The minor stadiums/outer courts are general admission. You can get a general admission which is cheap and you can see some good games. There are also big screens in the complex, so you can just sit on the grass and watch the main game on the screen (and have a drink or three).
Try
www.wotif.com for accommodation. Anywhere in the Melbourne CBD is the best, or along St Kilda Road is fine. There are trams to the complex and it is walking distance from the city. Again, depends on your budget.
Enjoy.