When I got my license I went for Auto as well, coz my dad bought me my 1st car and it was auto...
When i bought my own car, i bought a manual. I knew how do drive manual so I just went and re did my driving test.
Took like 10 minutes! U dont have to re-do the one on the computer again, just the driving test.
Was easy. Just call Vic Roads to make ur appointment