have you played Mobile Suit Gundam: Journey to Jaburo?
I would suggest you pick that up 1st ($10.00 or less used at EB or Gamestop).
If you like that get One Year War.
If you get through J2J you will get the basic story of One Year War (both games cover the same story) along with a basic understanding of the mission and goals.
One Year War is a hell of a Gundam game, best I have ever played and well worth $40 (I paid $70) if you are a Gundam fan.
I have no clue about a US release. Gundam vs. Zeta Gundam and Mobile Suit Gundam Seed: Never Ending Tomorrow were announced but no One Year War.
2. If you know the story of OYW you should get it. The gameplay is arcadey and really fun and the presentation is perfect. If you understand Japanese you'll get a lot more out of it as all the classic dialogues pre/mid-battle are awesome and totally engrossing.
My favorite Gundam game, and one of my favorite games this year so far.