Regardless of what happened to Fo Launcher, go to the Play Store with another computer, install some other launcher (any one for now), fill in the name/password for your Google account if the computer is on a different one than the phone, and that launcher will be installed into the phone. Then you'll get your choice of launchers. Choose the new one "Just this time". Uninstall Go Launcher, go to Play Store with the phone and install Go Launcher (the button will say "installed", not "Install", but it will still work).
Now restart and choose Go Launcher. If it works, hitting the Home button should give you the choice again, but choose "Always" this time.