JR Rail fm Tokyo Narita to Yamagata

This is my first time to Northern Honshu. I do not speak or read Japanese. I will be buying the JR East Pass. Please let me know what JR Trains to take, how much time it will take, how many changes i must make to reach Yamagata from Tokyo Narita Airport (the fastest way please). Thanks.

1) Narita Express from Narita Airport to Tokyo Station (1 hour)
2) Yamagata Shinkansen from Tokyo to Yamagata (2.75 hours)

You can look up timetables here:
http://www.jorudan.co.jp/english/norikae/

Hi guys!
Is JR East pass acceptable to any JR trains including shinkasen in all places in Japan like Tokyo, Osaka, Kyoto, Sendai, Yamagata? I read about this 4 days flexi pass that could be used both consecutive and non-consecutive days in a month; if I'll be using it on April 27 and 29 could I still be using it on May 15 or 17? Validy is 1 month so does it mean from April 26 to May 26? Sorry, if this sounds stupid but just want to make. Thanks for any reply.

Sendai and Yamagata, yes, but not Osaka or Kyoto. From the JR East web site:
he JR EAST PASS is not valid for the Tokaido Shinkansen and the Sanyo Shinkansen lines, which connect Tokyo and western Japan cities, such as Kyoto, Osaka, or Fukuoka.

More about the JR East Pass:
http://www.japan-guide.com/e/e2361_02.html

Thanks guys for your reply.
I'm confused about the validity period of this 4 days flexible pass. It says it's valid for a month but if I will use this pass on April 27 and 29, is it consider a month usage? or is it valid from April 27 to May 27? Please clarify. Thanks

It is valid one month from the date the pass was issued, i.e. the date you exchanged your voucher (if purchased outside of Japan) or purchased the pass (inside Japan).

If the pass is issued on March 27, it will be valid through April 26.

Thank you very much Uji.