Hey John H!
Check out this website and it will tell you all about it...
My mate did it last year as I didnt have the $$ on me then...so I was his "bitch timer" instead. Still pretty good fun though...
As for the cost...it doesnt cost much to get on, its just the after cost that you need to keep into consideration. The tyres(it will definatly wear down considerably), extra tank of petrol, transport (ie. ute - in case u fucked up and havent got a lift home to the city), food/drink...etc
It's definately well worth doin it...I'm just tryin to find another keen rider to go with as a back up for each other...just in case anything happens.(my mate is overseas)
If you're keen let me know, cause i was down the island on the weekend to catch a glimpse of the Yamaha moto GP test and the weather was perfect!! It definatly got my blood pumpin!!
Think about it as it could make or break ya!!