Integrated header and navigation across website

[3pixelchicks]

I have a php logo and nav that I want to incorporate across the entire site - including in the forums. I'm very new at this and pretty clueless, but I do have the header.php file that seems to work ok: www.3pixelchicks.com/header.php

I've searched the forums, and I think I need to add to add this code to a global start plugin:

ob_start();
include('home/www3pix/public_html/header.php');
$includedphp = ob_get_contents();
ob_end_clean();

I've activated the plugins, but now I'm stuck. I tried adding: $includedphp in the header template, but I'm not sure if that's right. It gives me an error message in the forum. Here's the error:
Warning: include() [function.include]: Failed opening 'home/www3pix/public_html/header.php' for inclusion (include_path='.:/usr/lib/php:/usr/local/lib/php') in [path]/global.php(383) : eval()'d code on line 2

If someone could let me know what I'm doing wrong, and which template (header? header includes? something else altogether??) I need to add $includedphp in, I would very much appreciate it! I apologize for being a total newbie here - it seems like the more I learn, the less I know.