The Namespace plugin was last used and included in version 2.5 (I think) released almost 2 years ago. Since then, we haven't installed it, and for a few versions after that release, we actively removed it during installation. So, you should uninstall that plugin altogether as it shouldn't be used.
The JFBCSystem plugin is installed automatically with any release of 3.0 and higher. If you don't have it, we'd recommend re-installing JFBConnect, which should upgrade/install that plugin. If not, you can install it manually by unzipping the JFBConnect file and installing it using the Joomla installer from the /admin/packages folder in the unzipped directories.
As for install instructions, we have a huge configuration guide, which should take you through the almost every common step. I think you're simply working from an old version or a incorrect upgrade from an old version, which is causing a lot of issues. We don't have a special guide for vBulletin integration as it's not a terribly common question, so we don't test that setup often or have a fool-proof guide for it yet.
Hope that helps,
Alex
Joomla and vBulletin
