changing from F-1 to F-2 is not a big problem. Your spouse needs to apply for a dependent I-20 to the international office. All you need is to show them that your spouse is in good status and you have enough financial source to live in this country during your spouse's study period. Once you have your dependent I-20 apply for the change of status. We will have your status changed with in 2-3 months. Good-luck