This question is good and dead, but there are a couple of reasonable answers. The heading 1 style can be directly removed in the Style Inspector (the button with a magnifying glass in the Styles panel). The top eraser button will reset the paragraph style to normal.
Another method is to create a new style from the desired formatting and then apply that to each paragraph. This can be done reasonably quickly by assigning a shortcut key to the style (then move through the document and re-style the paragraphs by placing the cursor in them and pressing the shortcut keys, no need to select to apply the paragraph style).