Arduino Duemilanove, connecting a digital compass

I have an Arduino Duemilanove board as well as an Oceanserver OS5000S digital compass. I have blunt cut wires for the compass that provide for an RS232 connection, and am connecting the Arduino board via USB. Does this mean I can't use digital ports 0 and 1 for the compass? Anybody have any suggestions on which ports to use or if I can even use this board? Thanks