>Do i administrate all these media servers etc from the master server gui 
or commands. If so do i do the device config there or on each media 
server with tpconfig?

Personally I like to create the initial configuration on a Windows Server or
UNIX Server with the local tpconfig command. (Long time NetBackup User and
UNIX CLI junky). The new device wizards in 5.0 for Windows and UNIX are
excellent, I am just stubborn and set in my ways. Once I have an initial
config I use the Master's GUI to administrate devices and make changes.

> i need to add entries into 
bp.conf and vm.conf, so say  REQUIRE_INTERFACE = <hostname>-mgmt

The bp.conf REQUIRED_INTERFACE can be modified remotely with the JAVA GUI
under Client Properties. BUT the vm.conf file must be manually edited
locally.

> Now the extra line of DEVICE_HOST=     worries me because i would have 
thought the device host is the master server. 

I really don't know what the DEVICE_HOST setting really does. I have not
noticed any difference with or with out it. You do need the SERVER = or the
MEDIA_SERVER = settings in your master's bp.conf. I have also noted that the
"SERVER=" should be the same on all media servers to reflect each other.
This is important if you ever plan to migrate media from one Media Server to
another with the "bpmedia -move" command.

> During install of media servers it asked which was the global device 
host or something similar to which i answered the master server, but i 
am not sure if this step completed or not. How can i check?

I use the command "tpautoconf -get_gdbhost" and "tpautoconf -set_gdbhost".
The master should be your GlobDB host unless you have a really really good
reason. 

I had a client once set up each Media server as the GlobDB host...
HEHEHEHEHE - LOL!!! Can you say Media Database Corruption and FROZEN TAPES!
Lucky for me he switched it back to the Master Server as the GlobDB host by
the time I got onsite, but he forgot to mention this juicy tidbit of
information while I was trouble shooting his problem!!!

> I currently cannot seem to see the media servers listed as media servers 
in the gui. 

Ensure the Media Server has a valid TPCONFIG... Perform a "tpconfig -d" and
verify at lease one drive is listed. Then recycle vmd and ltid on that Media
Server. Perform a "vmps -a" and verify "ltid, vmd, avrd" daemons are
running. Hopefully you will see "tcld or acsd" if you have a robot. Recycle
the GUI on the master... Create a Storage Unit in the GUI for the New Media
Server. Recycle the GUI on Master again. You should now see the Media Server
in the "device and media" sections of the GUI and in the "Media Server"
section in the GUI.

This is why I like to use the tpconfig manually. Unless the GUI can identify
the system as a valid media server you have a heck of a time administrating
it remotely from the Master Servers GUI.

I have seen media servers not appear in the Device Monitor window and yet
they perform backups flawlessly. This is usually a symptom of a corrupted
GlobDB.

Use the command line! It won't lie to you!!!

Just my 2 cents, ok maybe 3 or 4 cents...