Log into your iTunes Store account and click the Edit button. You'll be able to change the email address to which receipts are sent there. The iTunes Store never sends out credit card information in any emails they send, so you don't need to worry about that.
By the way, for future questions, this forum is for questions about iTunes U, Apple's service for colleges and universities to post educational material in the iTunes Store. You'll be most likely to get help with this issue if you ask in the general iTunes forums.