You don't need the extingusher or suit, but its up to you whether you use them. Your helmet sounds like it will be fine.
As far as racing goes, everyone is very friendly. You can just approach people later in the day and ask for a race, but firstly in qualify you just line up in two lines and race whoever.
Usually they run a DYO event where they handicap cars. So if for example you raced a 10sec GTR, you would get maybe a 6 second head start. Therotically you should both cross the line at the same time.
But I wouldnt worry about that atm, as this will all be explained to you there.
They have a drivers meeting in which they take new drivers out to the lights and explain everything.
Don't worry, its really quite easy.
Just some pointers....
Take as much weight out of your car as you feel comfortable doing. I usually take out the spare wheel, the jack etc as this is a bit of weight. As far as stripping interior, its a bit of work for maybe only 5kgs. Maybe take the passenger seat out. That only 4 (14mm) bolts.
Also, drop your tyre pressure at a gas station on your way out there, I found 15psi in 50 profile tyres works well. (take it easy on the way out there as 15psi is not a lot of pressure, so no hard cornering!) Only lower your front tyre pressure.
This improves traction.
Then theres flat shifting, launching, where to change in the rev range etc, but you shouldnt worry about that if this is your first go.
Just go and have fun.
Make sure your oil is fine and you are using 98 octane. Take care of your car!