I only had an initial Mastectomy with axillary clearance. Later I've had Breast Reconstruction with prophylactic Mastectomy to other side at the same time of surgery. PJ's with opening front were ideal. Probably short sleeves, as you will have an IV for a day or two.
I don't believe you have filled in your profile. Is your DMX for prophylactic reasons, possibly with immediate implants? Or is there a plan for Chemo and R/T? The advice may be slightly different. Have you been told how many wound drains to expect? I'm guessing 2 each side. The drains can be a little challenging, when moving around. Sometimes hospitals provide a bag to put them in, or a pillowcase will do. You could take a bag with a handle, big enough to fit equal to 4 large cans of food. I haven't found my breast surgeries too painful. Usually they suggest regular Paracetamol, with stronger tablets on top as needed. Don't let the pain get on top, ask when you start to need it. Make sure your Nurse Call Bell is always within reach.
I took a hand held fan, as I get hot too easily.
Do any exercises that are recommended for you, so that you can maintain a good range of movement.
Will you be expected to stay in/near Melbourne for a week or two after?
As Arpie says, accept offers for help, get on top of basic housework, preprepare some freezer meals, or buy.
Do you have friends and family that you are comfortable to talk to about your surgery?
Ask anything else.
Wishing you all the best with your surgery and recovery.