Well the previously state "solution" really is just
another way of doing it manually.

I would advise creating a style sheet that contains a set
of styles that meet your needs, including styles that
should be the same, but hve different names in the
different documents merely requires that you create a
style by that name, that is based on the desired actual
style.

Then by simply opening the documents, ensuring that
the "update document styles" checkbox is checked
(..Tools...Templates and Addins...[in Word 2k anyway])
then close the document, then reopen it...

Should make Word do the work for you.

In fact the only things that will leave out are:
  1: unstylized items
  2: header/footer size
  3: document page and section formatting

As far as points 2 and 3 are concerned, creating a
document "fragment" with the desired page and section
formats, then cut and paste (I can make that a macro for
you, if you want) the document content (as well as the
header/footer content) is the only way to fix that level
of problem.

If you have a lot of unstylized content, go slap the
author...send me some samples and I'll write the macro
for you.

I have over 600 macros, of which about 40 fix similar
issues.

Let me know how I can help.