GSM, GPS and Arduino

Hi guys im trying to start making a project using the GSM and GPS shield.... my problem is i dont know how to interface 2 shield in one arduino module...

similar to those projects that sends the longitude and latitude using the GSM module..

my other problem is what arduino module should i use in communicating a computer while there is a GSM module attached to the arduino... its like the GSM module recieves a data and displays it in a computer