If you have a large number of files that you nee to rename, it can be a real pain trying to do it in the GUI or on the CLI. The following script can be used to replace any character or string of characters in the name of every file in a directory.
#!/bin/bash ls | while read -r FILE do mv -v "$FILE" "`echo $FILE | tr 'STRING TO REPLACE' 'STRING TO INSERT' `" done
Just replace the red sections in the code with your desired strings.