Hi PAMS: If all you need is to change the wording, you can do it by updating the translation for the text. "Pay Now" appears in 2 modules in 17.0 - sale and account_payment. You can update the translation for the language(s) you need to change by exporting the translations to a .po file for each of those modules, updating the file and re-importing it. Please try this out in a test environment first.

The following link to a section in the Odoo 17.0 documentation explains how to update translations:
https://www.odoo.com/documentation/17.0/developer/howtos/translations.html#exporting-translatable-term

Hi,

Try to inherit the below template:

<template id="template_name" inherit_id="payment.submit_button"

              name="Submit Button">

        <xpath expr="//button[@name='o_payment_submit_button']"

               position="replace">

            //Add your code

        </xpath>

    </template>

Hope it helps