I read the forums and FAQs, and was able to accomplish, including my own header.php in the guestbook code (instead of the one provided). My header comes up and the guestbook appears as part of my page.
I ran into one problem I didn't see covered by the forums. My own header.php is strict HTML, except I had a snippet of php code inside it.
<? php
code;
code;
code;
?>
This code inside my included header.php did not translate and was not accepted. I finally deleted it so it would work. (The code only grabbed a random number to choose a picture randomly).
How can I include php code in the included header.php? Or do I need to split my header in to header1 and header2, and hard-code the php into the guestbook in between two includes?