Dryo, if you are going to RASIGS, you'll be attending the School of Sigs at Sale Victoria, for your IET training. I can't comment on US basic as I said, but at Kapooka you'll be attending for 6 weeks, plus an additional 4 (I think nowadays) "advanced basic" course for ARA personnel.
You will learn the joy of drill, get to experience "the challenge", which I've heard is considerably less than the 13k's we did back in '94' and understand that NCO's work for a living... Just learn to call an NCO by his rank, not "sir". WO's and above are sir...
You'll get yelled at a lot, get jabbed with quite a few needles, have a lovely looking haircut and get used to eating, showering, shaving, and dressing extremely quickly. You'll be placed under a fair amount of pressure at times, but remember, it's all a game. The object is for you to learn and pass. Not fail. Your instructors simply want to see you "putting in" and trying your best. That's all they want...
Snayke, don't worry about "training" for a shuttle run. It's a test of cardio-vascular endurance, not a test of how well you can run 6 metres... Just do a lot of normal cardio training and you'll be fine. Don't worry about your weight either. Running's easier when you're lighter and your running ability is far more important than strength in your initial stages. Keep it up with the push ups and situps.
The old "level 11" fitness standard as part of a soldier's AIRN (Army Individual Readiness Notice) compliance was 100 push-ups, 100 situps and a 2.4k run in varying times depending on your age, but typically around sub 8 minute 2.4k runs... If you can manage less 2.4k's on flat ground in under 8 minutes, you'll blitz the shuttle run...