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QFd MEL does have 2 piers, one handles gates 1 to 12 and then (what it is, can't place it exactly), but here is the link to the map of Melbourne Airport... http://melbourneairport.com.au/docs/130604-t1-(first-floor)-map.pdf
Hopefully it works out that the connection will be in the same pier!
Wear good shoes. Ones with good traction.
My plane from WLG was late into MEL, and I had to clear immi pronto a few months ago, had to run out from T2 out the auto gate, go up the escalators to T1 dom dep.
Lucky I had a pair of good shoes!
But for you OP, at least you don't have to pass dom sec twice, unlike VA system at MEL.
Is it QF617 and QF777, you can play around tomorrow to see which gate 617 comes into, and then which gate 777 goes out from.
MELairport website does not seem to give past info, on gates, but you should be able to see it historically tomorrow or today by now, at 14.20 to 15.00.