@
Sir Heroscape
, thanks for the answer... arf, a bit too much for my small collection ! ^^
However, I'm not in a hurry. I don't even have my material with me till the end of August. ^^
If I'm not wrong, you don't need to change the links. You just have to go to your files in Google Drive, Right Click on the file -> Share... -> Change from "Not activated" to "Can be modified".
Note : I actually have all this stuff in French in my computer, so the names are probably different...