If you want to update an existing gallery on your web server, you just need to replace the original gallery files with your modified ones.
If the typo you noticed is in a title or caption, then you need only replace the 'config.xml' file.
If you are in any doubt as to whether or not the original gallery files are being overwritten with your new versions, try deleting the original gallery files from your web server first before uploading the new files in their place.
After uploading the new files to your web server, you may need to clear your browser's cache before reloading the gallery to ensure that your browser is not hanging onto and using older versions of your gallery files.