At what stage are you running into that error?
The "yum update" is one of the first steps, but your output seems to imply you have some "kmod-VirtualBox-3.16.6-200" package from rpmfusion already installed that's angry about its dependencies?
What, exactly, have you done on this system? How have you manipulated the yum repos? What VirtualBox-related have you already installed? It looks like you've already installed something VBox-related from rpmfusion...what is it?
Installing VirtualBox is easy, just update your system, install the VirtualBox repo, and install VirtualBox. That is unless you've corrupted things elsewhere.