The latest version is 1.2.2. I just looked at the code for the affected files and it has not changed from 1.2.1 to 1.2.2 so it will work on either one.
Yes it is a mode to files. Yes it is possible that it will be overwritten in later versions - depends on what they change, so you would need to check out each time on a version update. Perhaps in an upcoming version they will make that filed Admin optional.
You will need to replace 3 files.
You can use cpanel or FTP.
Are you comfortable with doing that?