Hi Birder.

Melbourne Airport is easy to negotiate. There is one building (excludes Tiger LCC shed) - international sits in the middle between Virgin and Qantas. You'll be able to exit Customs, catch a lift or escalator upstairs and check-in for the domestic flight pretty easily. The walk isn't far, you'll just need a couple of trolleys. But not sure about porter service there to help given difficulties.

Virgin lounge at Melbourne is very new and nice. As Platinum, you and three guests will have access. After check-in, there'll be an escalator you go down and then turn left, entrance is then about 50m on right.

There's no differentiation re carry-on and status levels. It's seems to be policed very liberally, only issue may be if you hang out in the lounge too long and get on a semi full plane with lots of bin space already used. Virgin has priority boarding for Plats and Gold so you may want to take advantage of that, but if you miss the first call, it will usually just expedite your place on a packed aerobridge.

Cheers