I'm not quite sure what you're after but my own web site http://www.greentechnologist.org is an example of a "dynamic" cgi (actually mod_perl) web site. It's dirt simple. A single CGI sits at /wiki/wiki and I redirect the directory index for / to /wiki/wiki. Here's an (edited pathnames and mod_perl -> cgi) snippet from my apache conf. You might need to put this into a .htaccess file in an appropriate directory or something like it. Easy eh? The 404 page is actually just another wiki page so again - nothing unusual.

Redirect /index.html http://www.greentechnologist.org/wiki/wiki
ScriptAlias /wiki/ /var/www/usemod/bin/
ErrorDocument 404 http://www.greentechnologist.org/wiki/wiki?Error_404
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