JR Kanto Area Pass

Hi Japan experts!:)

I would like to ask a couple of question as this will be 1st travel experience to Japan.I will be staying in Tokyo fot couple of days and would love to visit a few interesting places in your country.My question:

1) I will be travel to Japan on 20th Jan 2014. Can i purchase the JR Kanto Area Pass (3 day unlimited pass)at the Narita Airport? If yes, can I use it immediately after bought the passes?

2) Will the pass covers my train from the Narita Airport to Tokyo?

3) I've seen the advertisment on the Gala Option Ticket and I would be very interested to take a day tour to Gala Yuzawa during my visit. Do I need to booked a seat for train to Gala Yuzawa ealier?If yes, what is the minimum day required to book?

Thank you in advance!