All models have the Tow "button" but that does not mean that it has the actual Big Tow package. The BT package includes receiver hitch, different gear ratio 3:36 (same as OR package), upgraded battery, pre-wiring for trailer braking, tow mirrors, tranni temp gauge and I think a larger tranni cooler. Without the BT package you are "limited" to the 7400lbs (give or take).
If you want to add a hitch then you will need to add a relay or two depending on what lights/trailer funtions you want to operate. By default the traielr brake lights and blinkers will work without the relays. Oh and if you don't already know, the trailer harness is attached to the inside of the rear bumper - should be a large plug with a cap on it.