I am sure there used to be a button that allowed you to show the header on page 1 and not the subsequent pages. Was i dreaming??
To the best of my knowledge, SurveyGizmo does not have such a button. However, one solution that may work for you would be to forgo creating your header in the Style tab, and to create your header in the Build tab on page one of your survey. An image element and/or text element, if they suffice for your header needs, would only display on page one of your survey, and not on subsequent pages
I hope this helps!