I went ahead and did it. I Imported an XML file of a large field group back to the same site I had just exported it from but only after editing the XML file, changing the null values of the Select fields and fmaking some field name changes.
I am happy to report that importing the updated XML file updated the fields with the new field names and new null configurations. This did not cause any loss in data or cause the data to get mixed up. The data that was already collected for the fields still display in their correct places on the output page.
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