Big Willow is billed as the Fastest Track in the West.
How fast do you want to go? So it depends on what you want to get out of it, a few NSXs have left the track there before; there are a few walls and some wash board & gullies to deal with off road.
It is Doug's home track so I suggest you look at the Pulp Racing site for some good info. Also there is good in-car video in the Pulp Videos. http://www.nsxfiles.com/
This is a place where you can learn the dynamics of high speed drifting the X. In other words, when you are at the limit thru turn 9 lifting presents some interesting problems.
Regarding passing; every group has its particular rules but the most common is only in designated areas (usually straights and very wide corners with visibility) and usually only after a point-by from the leading car.