Presumably you are planning to live onboard while doing the
work? Not many allow that.
The best know is Boatworks on the Gold Coast, with excellent facilities and numerous
marine vendors and services on site. They have courtesy cars and it's a short drive to get just about anything.
Closer to
Sydney, and a little cheaper,
Oyster Cove marina in the western end of Port Stephens may suit you. Old facilities, small
chandlery onsite, but the nearest shop is 5km or more away. You
will need a car. The last few hundred meters of the channel is fairly shallow so you should check suitability if you have a deep
draft.