Network sharing will be slow, but you can in fact store the music on a networked drive and do all your updating from whatever computer you like.
Well, if he has gigabit NIC's in each of his machine, it won't be so slow.
To the OP, I would set up a wireless/wired network. This entails getting a wireless router, but they aren't very expensive. Unless you go with an 802.11n wireless network, then there is a small additional cost. You'll have to let us know if your Macbook Pro has an integrated 802.11n adapter or any kind of wireless adapter. If that the case, then your only cost will be the router and the network cable to hook up the Vista PC if you want it to be wired, since it's stationary I'm assuming.
Microsoft also has a tool called SyncToy
. It's free to download from their Web site, and it's pretty powerful for such a small and simple application. It only works on Vista and XP, but it's still a good tool.
EDIT: To moderator, this thread should probably be moved to networking.