how to target (and change) an element that contains specific html.

how to target (and change) an element that contains specific html.

Hi,
 
I have a html page that contains a number of <H2> tags.  I need to find this specific <H2> tag:
 
<h2>Submit Your Survey</h2>
 
...and then replace the text 'Submit Your Survey' with something else (such as 'Click the button below').
 
How could I do this?
 
Thanks in advance for your suggestions!