Yes once you replace the factory radio it will stop working (won't even show the temperature anymore). I'm not aware of anything you can add to it but if you wanted to remove it and add a GPS that's possible.
Read through these DIY's
http://www.gencoupe.com/interior/54610-diy-budget-dash-gps-lcd-re-locator-install.html
http://www.gencoupe.com/interior/37304-installed-lcd-relocator-navi.html
Read through these DIY's
http://www.gencoupe.com/interior/54610-diy-budget-dash-gps-lcd-re-locator-install.html
http://www.gencoupe.com/interior/37304-installed-lcd-relocator-navi.html