There are a few different ways you could modify the php sample files in order to do this, and which is best is going to depend on the flow of your site and the expected user experience that you are looking for.
1. You could wrap the form portion of these pages in an if statement only to be displayed if the form is not submitted, that way it is only displayed until the form is actually submitted. Once the form is submitted, that portion of the page would no longer display as the POST array is not empty. This would work for keeping uses on the same page after submitting the form without actually showing it to them.
2. You could also add header('Location: http://www.yourdomain.com/successpage.html') instead of displaying the normal success message. This way when the form is submitted and a contact is successfully created, they would be moved to a specific page designed to handle the successful submission of the form. You could then use this page to display the success message and any other elements you feel are necessary upon creating or editing a contact.
... View more
At this time the CCSFG utility can be used to sign up new contacts, but does not update existing contacts. This is why you are receiving an error message telling you that the contact already exists. I have passed this feedback on to the developers of this utility. This functionality is something we are looking to add to the CCSFG, although I cannot provide an ETA of when that will be. We will certainly post on these forums when those changes have been implemented.
... View more