There is a TON of info out there on the Guard, presuming you are talking about Army Guard, and yes, I personally did a color gaurd last year for a local Guard unit shipping to Afghanistan from my home town in GA. Gaurd units deploy all the time.
As far as your other information you can join still in High Shcool at age 17, go to U.S. Army boot camp between your junior and senior year of high school, and ship to AIT and your job school upon graduation. I know lot's gaurdsmen, some of them I went to school with.
As far as training you recieve U.S. Army training for boot camp and for your job school, although you will do certiain exercises once you would get back, on your weekend drills with your local unit you joined with.
That's about all I know, contact a recruiter, or Ask one of the Gaurdsmen around the IMF, we have one or two actually.
"This conjunction of an immense military establishment and a large arms industry is new in the American experience"- Dwight D. Eisenhower , Jan 17,1961.