@ShadSterling @irenes @megmac @arstechnica GPS RF simulators weren't that expensive last time I sold one and I'd assume they are a bit cheaper now, so expensive for a repair shop but not impossible. But as you've got the phone open inserting messages pretending to be the GPS chip would work (unless that is integrated into the SOC?).
May also need to spoof a mobile tower to match the GPS location, WiFi too (but that is cheap).