You’d need a deck such as the Sony DSR-1500A which is about $5750 and an DSBK-1501 SDI option board for $1099.
SDI uses 75 ohm BNC cables – they are about $13.00 each for 6 feet length.
You need a computer that supports 64 bit PCI-X slots. The Dell XPS you mention does not have this, so you couldn’t use Decklink on that machine. You’d need to get a Dell Precision “workstation” class machine or a similar motherboard with at least 2 gb of RAM and a striped RAID of at least 2 SATA or SCSI discs.