94 chevy suburban deck

Sit in the driver seat, place your right foot on the accelerator pedal.  Directly above your shin, the amp is mounted to a bar that goes from the bottom edge of the dash to the firewall of the truck.  Remove the 7mm screws from the dash end and the firewall end of that bracket, the amp should drop straight down.  A Metra 70-1858 will plug into the wires that you remove from the top of the amp. 

There may be 3 screws, but that is where the tuner/amp is located.