Hi @DHuntRiverside,
you could export the records in question / or all records and do some cleanup work in Excel. Once you have the file ready with the updated Domain Names or Company Names, you can import them again to update existing records. The Record ID will function as the unique identifier. When importing, make sure to select the right settings when it comes to updating / creating new records and overwriting existing records.
I hope this helps.
Best regards
Colin