It's not hard to change your Apple ID. Just open iTunes on your computer, click the iTunes Store link, then click on your Apple ID in the upper right corner of the screen. Enter your password in the window that pops up and click "View Account". Then click the "Edit" button which appears to the right of your current Apple ID to change it.
Nothing needs to be repurchased. Apple still associates all your past history with the new Apple ID on your account.