How would I change these three things,
The Happy birthday, the "Please PM Jimmy" and the green bar with a broken image attacked
Well considering the fact that you're most likely using a 'ripped' or 'leaked' theme (I have seen that theme before with the same message which the 'ripper' put in place.
Well go to AdminCP Templates and Styles ----> Templates ----> your template then choose header and edit the html.
One question what's the name of the theme?