Hi,
I hope you will get an idea from all these projects.
http://www.engineersgarage.com/embedded/arduino/how-to-make-arduino-as-standalone-gps-receiver
http://www.engineersgarage.com/embedded/arduino/arduino-gps-interfacing-project-circuit
http://www.engineersgarage.com/embedded/arduino/how-send-message-gsm-module-using-arduino
The idea is to connect only the RX pin of arduino with GPS and only the TX to the GSM module. You can consider replacing the Xbee module in the circuit given in the following project with the GSM module.
http://www.engineersgarage.com/embedded/arduino/how-to-transmit-gps-data-from-arduino-using-xbee