Lets assume that you can still login to the admin of your site. Do so and change the password. Take a look for any other usernames - change their passwords if they are your usernames, delete them if they arn't
Now find the offending pages and change them back.
What system is your website using - just html pages or a CMS? If its CMS the so-and-so may have changed your template as well.
Thanks. My son built the website for me and he's dealing with it but I can't figure out why anyone should hack it and leave an e-mail address. Seems weird