If you look at the main macro, you will see a section that appears green coloured. That code is commented out and does nothing. If you remove the apostrophes from the start of each green coloured line that code will be run along with the rest of the macro to renumber the chapters.
To add your fixed code (which should be bookmarked in the source template also) locate the line
and immediately after it add
Code:
'Add this code
Set oRng = oDoc.Range
oRng.Collapse 0
oRng.FormattedText = oSource.Bookmarks("The name of the bookmark with the fixed text").Range.FormattedText
Put the bookmark name of the fixed text where indicated.