Cleaning Mass Data from a Survey

Hello!
I have been tasked with cleaning up the data from a survey that was sent out from our company to its employees. I am running into 2 issues. The first issue I am running into is if I export the data, then clean it up and import the data the support team has informed me that it would create duplicates, duplicates will really mess up our dashboards and results. The second issue I am running into is that If I export the data, clean it, delete out the old data there is no way to import the employee submitted images that are stored in the current survey data.
Is there a way around either of these issues or is large data cleaning not available through XM?