2003 Tahoe stereo aux inputs

I am installing a rear seat entertainment system in our new truck. The video is installed and I would like to have the option of playing the system's audio over the stereo. I know you can buy an FM modulator but I have not had very good luck with sound quality. My Tahoe came equipped with a Bose 6 disc in dash system but it does not have an external XM, DVD, or CD changer installed to use the auxiliary input. I would like to install an interface (like PAC AAI-GM12) to the data-bus to allow an RCA connection to the aux input.

Does anyone know if a GM dealer can turn on the aux input feature of my stock 03 Bose stereo?

I have the seim problem, if you faind hau to do it plis tell me Conny