To load the most recent org.el, always put it in the same location and
add this location to your load-path in ~/.emacs:

(add-to-list 'load-path "~/elisp/testing/org/")

Then doing a simple (require 'org-install) somewhere after this should
do the trick.  It will override any org.el that you might already have
in your .../emacs/lisp/ directory.

HTH,

-- 
Bastien