Here is a modified version of the search and replace tool, which replaces in the "Camera Label" metadata instead of the project item name:
https://www.dropbox.com/scl/fi/a2k14fndnqky8rdkli16y/Search-Replace-in-Camera-Label-Metadata.xml?rlkey=n42km2h9v54rhari80k7ixp2p&dl=1
You find it in the Community Library now at
Project Management/Metadata/Search and Replace/Search Replace in Camera Label Metadata.XML
All I needed to do is to open the block code of the Search & Replace in Project Item Names tool and repace the blocks to get/set the name propery with a block to get/set metadata. You can custumize it easily to use any other metadata column:

If you have issues finding particular metadata entries (i.e. they are not listed in the dropdown), see
https://docs.mamoworld.com/automation-blocks/tutorials-pr/metadata
To learn more about the block code for search & replace tools see
https://docs.mamoworld.com/automation-blocks/tutorials-pr/searchReplaceProjectItems
Concerning the second question:
There is no block to duplicate existing project entries (I think there is also no function for that in the Pr scripting API). So the only option would be to read the media path of the footage items and import the same files a second time. But this will import them with the default settings and not preserve any "interpret footate" or other changes you might have done on the project items. Probably in this case it is easier to do a manual copy/paste of the project items.