Swap two fonts in all styles in Microsoft Word?

"I think the only way of redefining propeties of a large set of styles in one go would be to automate using VBA.

What I would do here instead is redefine an underlying style (probably Normal rather than Plain Text, as Normal is the default for new text in a blank document) with the base properties of your document's text (language, Garamond font, size, line spacing and perhaps paragraph spacing) and change the other styles to be based on that.

This will give you more maintainable set of styles in the longer run.

If all your headings are going to be a different font, say Helvetica, you might want to set say Heading 6 as that font and base all other headings on that, but I don't think there's much need to use a much more complex model of 'inheritance'."

"If the inheritance from one style to another has been overridden explicitly with a different font in each one, you are stuck with changing it back in each one.
However, if this is a .dotx template, you could do this with some find-and-replace in the xml of the file which will probably be quicker than figuring out a way to do this with VBA.

Best book for any of this kind of work when busting open the 2007 file formats is Advanced Office Documents 2007 edition by Stephanie Krieger

Aside: while it won't help reduce the effort this time round, the 'right' way to change these will be to choose or create a theme font set, with your chosen font for headings and for body text. Then in your styles choose 'Georgia (Headings)"" or ""Comic Sans (Body)"" rather than the font face by itself. For lower-level styles base them on a previous one ideally (eg Heading 2 from Heading 1). Selecting the 'theme' fonts rather than explicit choices means that future changes are made far simpler by just changing the font set.

PS: please please please don't use Comic Sans for your body text."