OK Star -
I have 'grokked' what I can of Moodle's wiki and instructions -
Generally it appears you need to download and Install XAMPP for Mac 1.7.3 first and get it working - (by itself) to the point you can Start Apache and MySQL.http://www.apachefriends.org/en/xampp-macosx.html
THEN you need the current stable release of Moodle 2.2+ - (its another Mac Program installer - .dmg file) http://download.moodle.org/macosx/
I have to agree it (the how-to part) leaves much to be desired. It's so broadly vague, you may as well say "Good F****in' Luck" (as you will be needing it). There is, however, a spot for posting your Q&A'shttp://moodle.org/mod/forum/view.php?id=28
As its impossible to know 'how far' you proceeded - so I cannot say 'here's how to uninstall' all you have done so far. Suffice to say you should 'un-install anything doen so far'.
These are two separate packages - XAMPP is the Apache Webserver, PHP and MySQL server that will 'power' Moodle. Moodle itself is a CMS (Content Management System) built for coursework development. So (like WordPress, Drupal or Joomla) it 'sits on top of' the XAMPP installtion -