First thing you need to do is make sure that you have your head on straight, and realise that the racetrack can be dangerous if you do not know what you are doing.
I would do a performance driver training course before you go on track, and learn how the car feels, reacts and recovers from getting out of shape, then when you do your first event, go to Winton as it is the most friendly, wall wise, track in Victoria. Enter as a trainee, and ask for someone to sit in the car during the sessions to help make sure that you are not over driving or doing any thing silly. (You also will not be timed as a trainee, so there is no pressure to go faster than anyone else)
If you are only doing club level sprints, you need a CAMS L2S license, you can download the forms from the CAMS website at www.cams.com.au
To get on track you need an extinguisher, Helmet, clothing that is fire resistent (ie jeans, cotton shirts) and covers from neck to wrists and ankles, a secondary bonnet restraint.
Preping the car I would give it a full service with new, high quality fluids, put the best brake fluid that you can afford in the car, as well as good brake pads. A roll cage can be a good suggestion, but be aware that they can cause (along with bonnet pins) issues with road legalities. I wouldn't bother with R-spec tyres or major suspension changes at first, I would go out, learn the car on the stock suspension (as long as it isn't worn out) and good road tyres, and then go and speak to a suspension expert to get the most out of the car.