Question from a foreigner - buying stuff at an U.S. Apple Store

I purchased a MacBook Air in February this year and love it. I will be living in NYC for 9 months starting September. I'm considering selling my MacBook here in Germany because the money I'll get will probably be enough to purchase an even better newer MacBook Air in the U.S. (yes Apple stuff is more expensive here :) )

  • I see on Apple.com that the 13" with 8GB RAM costs $1,139.00. Is that price with tax or not? So will it cost $1,139.00 + tax? If yes, how much would that tax be if I buy one in NYC?
  • I can configure the machine to have a German keyboard layout online, but I would prefer to buy it at an Apple Store (it would basically be the first thing I'd do after landing). Can I buy an Air with a German layout at an Apple Store or could I order one online and let it send to a Store to pick it up?