Trackdays are around £450-500, but for that you get full track stewarding, open pitlane for 8hrs, no queuing, only cars ie. no bikes, lorries, buses, campervans etc, re-fueling on-site, some free tuition if you need it, sighting lap. They are the best way of safely doing the ring as most have experience and all get a safety briefing and rules to adhere to on the day.
Tourist days are a free for all and are more daunting than an organised trackday if you haven't been before.
The link below is the one I've been to before.
http://www.destination-nurburgring.com/datesOr Circuit-Days have one too..
http://www.circuit-days.co.uk/nurburgring.asp