What MOS is this?
Unless you are in the AF I don't see you having enough time to do all you mentioned here.
I know I tried when I was in the Navy not to mention the "mindset" isn't really all that conducive to programming from what I remember.
But yeah you'll want to learn C# if you plan on using XNA since it's the preferred language for XNA.

I don't have an answer for you, but I just want to say that if you do decide to go with a certain book, read the reviews it got on Amazon before buying it, and try to see if it has any sample chapters available to get a feel for it's writing style and if you like it.

For example, this book probably has the most amazing games ever shown in a game programming book, but most reviews say it's rather poor, especially for a beginner (although the 2nd edition should come out in march, maybe it will have some improvements).

You could do a search on amazon for "XNA" to see what's available and look inside some of the books.

Being as you're talking about MOS and AIT, I'm assuming you're going Army, correct? (Air Force and Navy have different acronyms and languages for their job/tech training, and you wouldn't be asking this if you were going into the Marines)

First of all, forget studying anything but what they want you to study at the very least until you get to your first duty station. Learn what they want you to learn in the meantime and use any spare time you have (there will be precious little of it) to catch up on sack time and call your folks. Trust me, I was Air Force, and even we didn't have all that much spare time in tech school. It wasn't until I got to my first (and incidentally only) duty station that I had any time to myself whatsoever that wasn't taken up ironing uniforms, shining boots or some other chore that needed doing.

That being said, I'd wait until you're in a position where you have the spare time to bother buying any books. You'll have at least a couple of days/weeks after AIT before they ship your butt to the sandbox. Ask again then. *grin*