Yes, connections to the sound card are needed to work PSK and other digital modes. A serial connection can be added to the same com port for CAT control if the software has CAT control feature like MixW: http://www.mixw.net/
Add a resistor pad 10K/1k to the transmit audio and use low power levels to keep from causing interference. Interfaces can be made or purchased for interconnection to the radio and computer.
One site is: http://www.packetradio.com/psk31.htm
Also read the TS-2000 manual part about external TNC set up to activate the interface.