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The best way to do this is to use the CleanImport plugin because that will purge the catalogs of existing settings and add your new template's settings instead. Using the Frame Import > Formats will just add the new settings on top of the old.

In either case, you'd open the book file, select all component files to which you want to apply the template and then either run the plugin or do File > Import > Formats. If you use the FM process, there are checkboxes to Remove overrides... which you should activate.

For follow up, you need to reconcile the old settings, which you can do by copying one of your new paragraph tag's formats (Copy Special), and then searching for the old paragraph's name and replacing it by pasting from the clipboard. At the book level, obviously.

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