If you want to replace one paragraph tag with another, do the following:
1. Use the Copy Special > Paragraph Format to copy the new paragraph to
2. Open the find and replace dialog box.
3. In the Find drop-down menu, select Paragraph tag.
4. In the Find field, type the name of the old paragraph tag.
5. In the Paste drop-down menu, select paste by (this means that whatever
is in your clipboard will be pasted in place of the old paragraph tag, in
this case cause you copied the new paragraph format to your clipboard, the
new paragraph will replace it.
6. DO NOT do a an All change.
7. Make one change to verify that it is working.
8. THEN do an All change.
That should convert all your old paragraph tags in your book to the new