[chirp_users] Programming question

Friend bot an 82C.  Wanted to make some changes to what he programmed so sent me the *img file.  I opened it in Chirp and made the changes.  When I went to send it back I cannot seem to have the file save the changes I make - it simply reverts back to the "old" file.

-  Is the file unique to him and his radio so I am unable to make changes on my PC and have them saved?

-  Do we need to use the import/export function to make, save and reinstall the corrected program?