.im files are not editable unless you are the creator and exporter of them. You can view these files with a tool called "File view(er)" I think, a forum search will give you an answer. Technically, yes they can be converted, sort of, to be manipulated/edited to a degree, of what I read here in this forum but this is usually not talked about here as this is rightfully frowned upon. (Only typed here for those who like to correct statements)
.gs files are script files, one can read these with Note Pad for example or other text viewers. Sometimes scripts are "scrambled" so they can not be viewed if the owner/user of one of these does not want them to be copied and used by others. I usually place ".txt" on the end of such files to view or in the explorer menu you can "open with...." these files.
Btw, these files are not hidden, one can see them everywhere in the game.