If you have already have requalified for a car license, you just need to sit the VicRoads Boat License theory test. Do not say yes if they ask if you take any prescription drugs... I was truthful and ended up with my car license almost suspended as I'd been re-examined for the car 33 years before and they didn't ask that back then. I had to get all types of proof I was safe to drive which 'red flagged' Marine Safety Victoria who then tried to stop me (a C6 quad) from getting a boat license for my 25' yacht.
If you just sit the theory test, pass, and don't complicate matters by answering any question other than how you are paying for the licence

then you are fine. Get tied up with Marine Safety or VicRoads red tape and you'll regret it. Best of luck.