You may have to go to Afghanistan, but it's a lot better deal than Iraq, IMO.
Due to the location of the deployments, this is not for Australian service personnel. Leaving aside the injured, we've had six soldiers killed in combat in Afghanistan compared to the one (aircraft crash, IIRC).
To the OP,
Good for you if you're joining the services. Just remember that whilst you may be going in there for reasons of self-interest (life-long desire, paying-off university debts, career, etc) there quite possibly could come a time where you are then required to sacrifice. Understand this and be cool with it before you sign up.
Secondly, don't be fooled by the adds. They may show people rebuilding villages or giving vacinations to children but you need to remember that, at it's heart, the military is about violence. Consider this carefully and, as above, be cool with it before signing up.
Finally, make sure you know what you want to do before signing up for a lengthy return of service; if you're not so sure, you can't do worse than signing up as an enlisted man and picking up a trade (which, I believe, is what you want to do).
At any rate, whatever you do, good luck.