Hi Diggs,
I'm by no means an expert here, but I'll do my best to help.....so any one who is more proficient please do correct me if I am leading Diggs astray!
1. You should be able to connect your BS1 using an airport express base station as per the following link to stream music. My setup is quite simple as its just 2 audio systems and I currently just use a mini jack to din cables (same as used for an Ipod connections) to connect from the airport to the system Tape/Aux. All my music is now saved in lossless and really does sound very good. An external DAC is under consideration for further improvement
Your BS 1 has digital inputs, that means that to get the best results you can use the digital optical out connection from the airport base station (its the same as the mini jack actually) to the digital coax / optical input on the BS 1 ....
http://www.apple.com/airportexpress/
I'm not so sure how the video will figure into this setup ... are you planning to play this also from the G4?.... as I haven't set up for this, but as BS 1 is an AV processor this should be able to be worked out once you get it all connected. You may have to use AppleTV though if you want to be able to stream the video, which therefore means that you can probably do without the airport express base station as the AppleTV can stream both as i understand it ..... Perhaps another member can assist here?
You could also check out another of soundproofs threads... this may be clearer and or do a search on beoworld for other threads...Specifically the Beo / Mac section.
http://forum.beoworld.org/forums/p/19674/146656.aspx#146656
Of course you can connect the G4 with cables, but again I'm not sure on the connections required.
2. Once you have the airport connected you'll need to use airport utilities in the applications folder (you may need to update as I did for mine, go to apple), this will allow you to find the base station on the wireless network and get it to join the network, when doing this you can call it for instance 'living room', once done you should then be able to see at the bottom right in itunes speaker options "living room' and you should be able to select it... music should follow..
3. If the hard drive is a network drive yes I think you should be able to connect directly to the router. I haven't done this yet, and strangely a friend in IT recently recommended a Western Digital drive to me. You can then transfer all your itunes library to the drive, I would recommend one that mirrors itself so in the event of failure you have a back up... When you do this you will need to adjust in your preferences where your library is located. Again go to apple and search and they have a description of how to do this.
4. To use the Iphone as the remote, simply download iremote from apple onto your G4, then sync the iphone. When the iphone is logged onto your wireless network , you launch the iremote and its simple to set up and once done it will always automatically search for your library and connect...
Well I hope that this is of some assistance.
Laurence.