AMA card a definite ( you get a free magazine sub anyway).

The ESC will be determined by the draw and size of the motor you will run.

The term "shooting someone down" means that you are on the same channel as someone else at the field and are affecting the other persons plane.

Do yourself a favor and call Hobby Lobby. Ask for Ben or LA. Tell them what you want and ask them what you need. They can answer any question you have and are great people to boot. I'm sure they have everything you need.
http://www.hobby-lobby.com

If I were new to this hobby I would buy a Zagi. A Zagi is a foam wing with two servos, rx, esc and a 400 motor. It is really fun and if you ding it into the ground (which I have done at full speed) you won't hurt it. It is really easy to put together as well. I know it doesn't look like a real airplane (it is based on an actual plane). It will teach you how to get oriented to the plane coming at you and going away from you. There is nothing worse that flying the plane you just built into the ground on your first flight (and the chances are good that you will). I was also a lot less nervous flying something that I knew I could crash and not much would happen. If you have any questions feel free to email me.
Go here to learn about the Zagi:
http://www.trickrc.com/
Go here for tips to build it:
http://www.yourzagi.com
You can check out my Zagi here (at bottom of page)
http://www.secondsight.com/rc