but somewhere in my config I've broken things so that gpsapp doesn't run and when I turn my GPS on my player goes into freakout stop-pressing-so-many-buttons mode when the gps starts sending packets.

If I recall correctly, you didn't do anything, hijack changed an option. Go to DC mode and change the "serial port behavior" option in Hijack's main menu. I think you are supposed to change it from "player uses serial port" to "apps use serial port". Or something like that.