Yes the 'box in storage' on the passenger side in the rear is the On'star/GPS control unit. On mine theres actually two boxes. From what I have heard/understand, everything from 2001 back (maybe higher than 2001) uses the old GPS analog signal or something, (point being they no longer function), and can be removed. I have also been told to 'flip' the antenna down if running through an automatic car wash. (I wash by hand)
Just some FYI

 

Ok thanks man.