In the example here uart 2 is configured rtcm3 IN and nmea OUT at 115200 if your xbee module comes from ardusimple it is configured at 38400 to switch it to 115200 follow the link Changing the baudrate of Ardusimple Bluetooth module - ArduSimple
Use guidance systems that accept nmea 0183 messages in rtk mode with f9p simplertk2b