Hey! So there's some metal in Sin City? Excellent! Glad to have you aboard.
Just a suggestion, but I'd recommend not booking a hotel for the days during the festival. You will not spend enough time during the night to justify the cost, believe me!
Start your bookng after the festival's over so you have a chance to wash three days of Wacken mud off and return to civilization.
If you can rent a car, sleep in it at the festival - you'll get more sleep that way, haha. An RV would be great, if it can be managed. Though again, you're coming during high tourist season, so they'll be in short supply.
I'm working on a website together with info and hints for American metalheads thinking of making the long pilgrimage to Wacken...I'll post something here when I have it up.