Prelim Dates are now out but not yet set in stone :-
http://www.nuerburgring.de/events.286.0.html
They coincide with my plan though so track time as follows :-
* Saturday, 03.05.08 17:30 until 19:30 h Touristenfahrten, 03.05.2008 (Nordschleife)
* Sunday, 04.05.08 08:00 until 19:30 h Touristenfahrten, 04.05.2008 (Nordschleife)