It may help you to reverse what I do to clean up documents when, as in your
case, wiping out all formatting is not an option.
Turn on keep track of formatting in Word options and go to styles pane >
Options (in W2007). In the section of the dialog that says "formatting to
show as styles" put a check in the box before Paragraph level formatting.
Create a normal paragraph and apply formatting (say 14 pt bold ) that is the
same as one of your user-defined styles. An entry will appear in the style
pane that says something like "+ 14 pt bold" ("Normal" does not always
appear. For other styles with manual formatting, the style name always
appears before the plus sign.)
In the styles pane, select all instances of the user-defined style you
duplicated, then apply the normal + formatting you just created.
Do this for any style that you want to change to normal + formatting.
Note that this will break your heading numbering, so my may want to convert
those numbers to text before you begin. As an aside, I have found that
using multilevel list numbering linked to styles, though sometimes tricky to
set up, is a reliable and easy way to apply and fix heading numbering.
HTH,
Pam