If he's renting the server from a server company it might cost him more money to get SourceTV. From memory the provider I used to use a while back charged an extra £5 a month or something like that. Just thought I'd throw that out there.
Yeah, that's certainly possibly and you would also need a slot for it.
Nfoservers, where I rent from does not charge extra (aside from the extra $1 per month for an added player slot), but any server being used for comp (at least in UGC, don't know about other leagues) requires STV to be on the server for opposing team's players and to record an STV demo, this may not apply if the server is only being used on this site though ...
I assume the slots are not an issue since you want to spectate which would take a player slot anyway so maybe just look into weather or not your server provider charges you or not. If it does not then that might be the easiest way to do it, in some cases it is as easy as clicking a button on your web control panel for the server to activate STV, depending on your provider you may have to use .cfg files to activate it on the server, so depending on how much you know how to do through ftp with .cfg files on the server it could get a bit complicated but ultimatly isn't too dificult once you figure out which file the commands need to go into.