I need to modify a template from a third party extension to match my current theme. In the extension layout xml file
app\code\IWD\Opc\view\frontend\layout\checkout_index_index.xml
<action method="setTemplate" ifconfig="iwd_opc/general/enable_in_frontend">
<argument name="template" xsi:type="string">IWD_Opc::onepage.phtml</argument>
</action>
I can either change the template path in the layout xml file, or edit the onepage.phtml. But I don't want to change the original file. How to do it the right way?