I discovered that you can't upload a file to the Repository, then edit the file and upload the updated version using the same name. The File Picker triggers an error message "file already exists" when you try to select it from a File System folder.
The only way to select the updated file is to rename it and then FTP it to the File System folder, Then the File Picker will let you select the updated file.
But, the OLD FILE is still in the database with no way to repalce it.
There should be a way to overwrite an existing file in the repository.