What you have done will work but we can add the “Swedish” language in the plugin. I will send you a language file for you to translate and then I will add it in the plugin.
When you modify the language file you need to make sure that they are saved as UTF-8 format otherwise the accents won’t appear correctly. There are a few text editors that can convert to UTF-8 format. I use the PSPAD editor for this (http://www.pspad.com)