I'm not sure about grades... internally, a C average will generally get you into Japanese, but I imagine it's a bit different for those wishing to transfer from different universities.
Also, those with prior Jap study usually have to sit some sort of competency test (to gauge which level of Jap you should be placed in).
Umm... Performance is a very particular area of study (which I know nothing about).
You're best to contact people from that department directly so you can get quality information.
I can provide you with a few links to get you started:
http://www.arts.monash.edu.au/future/http://www.arts.monash.edu.au/ecps/future/index.phpIf you are unable to fully tranfer, you could enrol in a Diploma of Languages for Japanese @ either Melbourne or Monash (@ UoM it's called a "Diploma of Modern Languages").
You can claim credit for the Jap units you've already studied, so you shouldn't be forced to stick around uni any longer than you originally would have.
It sounds like this is what VU is suggesting you do, unless they've got some sort of special arrangement with UoM.
Links for Diploma:
http://www.arts.unimelb.edu.au/currentstudents/programs/DML.htmlhttp://www.arts.unimelb.edu.au/futurestudents/programs/credit.htmlhttp://www.arts.monash.edu.au/future/apps-undergraduate.php (also see the "Undergraduate Diploma Application Form" - 3rd link in box on right-hand side of screen)
Regardless of what you decide to do, try not to delay your inquiries and applications and such... you may miss deadlines you don't know about.