yep agreed with dh.
as iv said, track insurance doesent cover you cause its a public road (unless your doing a track day), and normal insurance doesent cover you 99% of the time cause the nurburgring is written out of your insurance.
there was a german temp insurer (not sure if there still around or if there policies have changed) however as part of there temp insurance it covered you on the ring on a normal tourist day. not sure how much cover you had like.
and as said, if you crash the cost of the car is the least of your worries, even if you dent a 1m peice of the armco, you still have to replace a whole length (around 10m iirc) and at somthing like £60 a peice + fittings + installation etc. (baring in mind that pretty much the whole way around the armco is 5 peices high, so if you dint a 1m peice chances are your going to be replacing 5x10m peices at £60 odd a pop). then if you need recovering its a stupid price (circa£300), and if you need recovering they shut the track and you get charged for each min the track is shut.
so even if you come off the track, gently bump a peice of armco and damage the steering rack meaning you need recovering, chances are your bill is going to be >>£1000.
hopefully you will be ok, when we were there there was only 1 crash in 2 days (although quite bad, fliped the car a few times and bounced over the armco (actually bounced over it so he didnt have to replace any armco...)) but that shut the track for 2 hours so he proberbly still got a large bill...
either way enjoy it