I went there last October when I had my VX220 turbo, as others have already mentioned it is an amazing place and unlike any other race track anywhere in the world.
The thing that always makes me smile is that any track day in the UK you will have a 30 min safety briefing etc etc, at the ring you turn up, pay for a lap and go, no one will talk to you at all and all the marshals are looking for is that you car is road worthy.
We stayed at www.hotel-an-der-nordschleife.de
Really nice clean place good showers, right by a good watching corner and a 10 min walk from the town.
If its your first time, just take it easy, personally I treated it like trackdays in the UK, if there is a bugger on your bumper just let him past, don't go racing anyone and just keep a clear space around you and you should be fine.
I only had one 'moment' second lap and it started pouring with rain and in the section of left right curves just after the main straight the offside rear wheel touched the curb, the back of the car swung round really quick and I almost binned it, luckily I caught it, things settled down and I did the rest of the lap with my heart pounding in my chest and I really was not going that quick.
Have plans to go again this year and I have been wondering how the Z will cope in regards of brakes and what sort of upgrades might be needed, the VX being so light was completely fine as standard.
I would say definately go and just be careful, take it at your own pace.
Also, for those who love GT4 and the like, apart from giving you an idea of which way the corner goes next it is nothing like the real thing and the way the track goes up and down.
You also need to be prepared to get totally wasted by local Germans in rust heaps who will pass you like your standing still.