Q: how do I remove my credit card info without resetting my ipad

Your credit card is linked to your iTunes account not your iPad, so resetting your iPad won't affect your account's payment details.

On your iPad try tapping on your id in Settings > iTunes & App Store and selecting 'View Apple ID' on the popup - that should give you a payments link on your account's page. Or on your computer's iTunes you should be able to edit your payment info by going into the Store > View Account menu option and logging into your account, and on your account's details page there should be a payment link.

Changing payment info : http://support.apple.com/kb/HT1918