import vbulletin data into joomla kunena

I have a Joomla/Jomsocial site and am running Kunena for it's forums. I have a vbulletin site with 11000+ members and I want to import it's data into Kunena. I want the posts, images and members that aren't already in jomsocial/joomla. Basically, if the member already exists in jomsocial I don't want their member data to overwrite it, only have members not in it to be added and those who are already in jomsocial have their posts on the vbulletin board be attached to their profile in jomsocial.