Making a form disappear for returning visitor

Hi -

I'm embedding a form into a page, and I have two questions:

1. How can I have the form be replaced with a "Thank you" message when it is submitted?
2. Once a person has submitted the form, how can I make that form disappear the second time the person visits the page?

I found this page that hints at ways to alter the form on submit, but I'm not sure of the specific steps to accomplish these tasks:

http://developers.marketo.com/documentation/websites/forms-2-0/

To be clear, I don't want to take the user to a Thank You landing page - I just want the form to change to a simple text element saying "Thank You". And then not show on subsequent visits.

Thanks for any help you can provide!