Hey Jigsaw,
I copped a 41 raw for JSL last year and I had no previous experience with Japanese language and culture.
The key is to ensure you embrace yourself in the language as much as is possible. There are now japanese shows on netflix which would be a great downtime activity (my advice with these is to watch it with japanese subtitles on if available) and I found it HUGELY beneficial to go to language exchange sessions where you have an opportunity to talk to native speakers (VERY HIGHLY RECOMMEND). I have been going to one called Japaneasy in the city (
http://www.japaneasy.com.au/language_exchanges/) and still go to this day to maintain my Japanese post-VCE.
Basically although it is a significant amount of work, I didn't feel it compromised my other subjects and it was a nice balance to have .
Good luck! And let me know if you have any questions