Set up a development server (as Greg
Hewgill mentioned, VirtualBox and
Virtual PC are good choices for
this).
Put the current site files
(including the relevant web server
and PHP configurations!) into
version control.
Find out what files are being used -
use your development server setup to
test by removing all the fooN.php
files and see if it still works.
Pray...lots (OK, this isn't
required, but it sounds like you'll
need it).
