winton fun days are just show up, pay and get scruteneered and away ya go.
They getting pretty busy though so you really need to watch your mirrors and be carefull of dickheads that have no idea.
as for the noise, trust me. DONT WORRY. there have been a number of days i went to a around 18 months ago that ex v8 supercars (ea falcon) have been out testing along with hq race cars, open wheeler formula fords and a gt3 (once)! trust me, no skyline is as loud as them.
if you havent been to a track day i highly reccomend it, unbelieveable fun the first time you head out and think...... holy crap...... im on a race track!
if you are planning on having a bit of a dip make sure your brake pads are healthy. also reccomended that you give car a service afterwards if going hard.
fuel is available at the track but is expensive, 100 octane is on pump too!
hope the info is helpfull
enjoy
brett!