VOX

You would need to do the PBX install first, though I don't know for sure if it is included as part of the normal install.  According to the install guide if you need to do a separate install it will prompt you. Like ayodeji said, you do not need any...

The install for a master and the media are the same, so yes the files are there.  Check out the install guide, it should get you started on the right track: http://seer.entsupport.symantec.com/docs/290199.htm

If you have a Master server up then you don't need to install anything else to make it a media server.  You will need to setup storage units to actually use it like a media server.