The Saga of Adding a Navigation System

I have the 2004 Z71 Tahoe and I am trying to add an aftermarket navigation system. I purchased the PIONEER AVIC-N1 (which has a tuner) from Ultimate Electronics, along with 3 modules to hopefully enable the same functionality as the factory radio. However, after spending 3,000 (including tax, labor, cd changer and the modules), we discovered that that the rear, 2nd zone tuner would not work. Back to square one...All I really want is to modify dash to install a nav system, without it conflicting with the factory radio. Has anyone done this? If so, please let me know what system you installed. I am not very handy, so I will be paying someone local to do the work. I have even investigated the car p.c.'s, because they have gps with navigation functions.