I'd try for a safe lap on your first visit. Once you know the layout, totally different in real life to any video game, then try adding a little speed. If you do better than a 10 min on your first day, be happy. If you beat 9.30 then be content. If you beat 9 minutes then you have driven a lot on tracks before. If you beat 8.30 you are a god and I will have your kids.
I've been taken round in an Elise 160 in 8.35, two up of course, and the driver had done over 600 laps.
Also 7.53 in an M3 CSL and the driver apologised for going slow due to traffic. He had done over 1,000 laps.
I get 9 min +'s out of my stock 964 and always walk away with a smile.
The key to the ring is walking away. Forget time. Enjoy it.
I've done over 100 laps at least now and have just bought a Skyline to learn it more during 2008. Planning 4 trips this year and hope to double my lap count.
Look forward to seeing you there.
PS - Stop after every lap or every other lap to let the breaks cool down. I drive down to Brunchen and watch for half an hour. It is good to have a break and also to let the nerves and the car recover.
See Ben Lovejoys' site. It is the bible.