DV uses 3.6MB/sec so for 1hour of video you'll need 13GB of disk storage.

as for firewire cables I can only speak for myself, Ibought a cheap firewire card for £10 and it included the cable and I've never had any problems.

You will probably want to add more ram to your system as well, you'll really need a minimum of 512MB but preferably 1GB. Video editing is really demanding.