How do I search the support for Register Plus Redux?

Once I have acquired the data with Register Plus Redux, is there an API I can use to get the data? I know what table its in but it seems like there should be some functions for this already. It isn’t in get_currentuserinfo() or get_userdata()

This is a poorly documented feature, I agree. Regardless you would get to it using a WP_User object. If you added a custom field gender, you can access that property on the WP_User using the following syntax. $user->gender

No, its not in the WP_user object. However you can get it with get_user_meta($userId);