Yeah, getting a school will be hard, and very expensive, getting the visa will be hard too.
Doubt you'd get credit for going to a Japanese school unless your japanese is good to start with - i didn't get any credit and neither have any of my friends past or present for going. Mainly cause theres nothing to get credit for and we didnt really study the subjects (just japanese).
My suggestion would be to start contacting schools now. You have a friend in Japan? Good, ask for her help, start sending out letters to school explaining that you would like to be an exchange student at their school, see if anywhere is interested in letting you attend.