Recently when trying to modify the success.phtml section in magento, I found it very frustrating the fact you had to make new fake orders to see your modified file. Of course I could have used firebug or some extension like that but I much prefer making modifications and hitting refresh.
After a little digging into the core files, I managed to find a solution.
There is no need to move this file to local (unless you have already modified this file, so use the local version instead) as it’s only a temporary modification, obviously you don’t want this on the live site so *remember to undo this change when finished*.
Change: (Line:227 in 188.8.131.52)
Simple as that, hope this helps.