You can't edit skins like that. You need to recompile them again and change the directories. Here's a guide now to do it and i think it should work these days. I haven't done skins since 2006 so i don't know anymore. http://www.mani-admin-plugin.com/joomla/index.php?option=com_kunena&func=view&catid=12&id=4434&Itemid=128