You can change this in the language file for the template (en-GB.tpl_gk_yourshop.ini), actually you should translate the whole file and then rename it to xx-XX.tpl_gk_yourshop.ini and then copy that file into your joomla language directory on the server.
Be aware of special characters when saving the file as you sometimes need to save language specific files with the UTF-8 format or even UTF-8 NO BOM. The text editor UltraEdit can help you with that job.
But as with everything else there's always an exception ad VirtueMart language files are behaving differently in my experience...
Hope this will get you on your way!