Hi Dick,
You are not going to be able to interface your serial gps device to SCXI. To use your GPS device, I would recommend interfacing it directly to the serial port of the PC or even better yet use a PXI-1010 or PXI-1011 combo chassis instead of a PC. These chassis combine an industrial computer and expansion slots in the PXI format along with slot for plugging in SCXI modules such as the 1102B. For more information please see:
http://sine.ni.com/apps/we/nioc.vp?pc=bypc&cid=1525〈=us
I hope this helps. Good luck.
-Steve