Update texture of the inside of a sphere where the user is looking (Android)

Hello, complete OpenGL for Android newbie here…

I am able to display a texture on the inside of a sphere. Now, I need to update the texture (likely using x,y coordinates) at the place where the user is looking. We are fiddling with GluUnproject but we can’t quite figure out what to do with the return x,y,z values we are getting (or even if they are correct.)

Could someone point me in the right direction for getting x,y coordinates to update the texture?