Remember that the track is basically a public toll road which resuilts in loads of serious accidents,
also there are long queues on most public days especially if the weather is good and if it is a public holiday or at weekends.
There are many, many clubs that organise private events and these are much safer and better than the public days and are easy to sign up to.
I personally would not go out on a public day.
This might help you understand better what I am trying to say.
http://www.rmatrackdays.com/?id=nurburgring