While at it - a small nit w.r.t to the otherwise cut-and-paste perfect:

http://www.observium.org/docs/install_*

pages — a config for apache

DirectoryIndex index.php

should be added; either global or, better, within the <Directory … blocks. As it is no longer part of most php default installs.

Furthermore - if you want to be very safe on modern unixes - adding a:

SetHandler application/x-httpd-php

is not a bad idea; and otherwise harmless; as some now avoid this by default for security reasons.

Dw.