Basically, check the first post. CAMS is available on the day; $50 for L2NS (texi events, etc) or $100 for L2S (speed events like EC, etc). I got L2S and scored like $140 off my comprehensive insurance, so I was $40 ahead, winner! You'll need a fire extinguisher as well, Autobarn have them for $30 or so. I've used the bolt that holds the passenger side of the rear seat down as my bracket mount.
Scrutineering is basically to make sure everything's ok, fire extinguisher is there, nothing loose around the cabin, no oil leaks etc. If your 3.5" turbo back isn't too loud, it should be fine. Basically, as long as it's not one of those ones that people 400m down the street go "here comes that asshole again", you should be right.
Helmets... You can actually get them quite cheap, I got mine for $100 inc post with two spare visors.
http://cgi.ebay.com.au/FULL-FACE-MOTORCYCL...=item35ad82ffb2
Check this guy's stuff out, and make sure to measure your head if you're gonna get something from there. The dark tinted visor he also sells (not mirror) is quite good, too.
But by far the BIGGEST thing you will need is a desire to destroy tyres and do fast times