Update Source and Type of Authority Document

We have a requirement to import some of the national guidelines as authority documents and our parent group company guidelines (we are an afflitiate) as authority documents to GRC.

We have imported those authority documents via excel import and now it is in production. We need to change the source name and the type (this is a dropdown field) to different naming conventions as per our usage within the company. 

Advise me

1. how can i do this for existing production records?

2. will there be an impact in future?

3. How can make this reflected in future excel import