Where is the thermostat on the 6.7? Is that the sensor right behind the radiator on the left side just infront of the EGR crossover?

 

Just follow the upper rad hose, it will take you right to the thermostsat housing. It is under the EGR stuff (deleted on my truck), and has a metal heat shield on it, too.
There are 2 sensors on the thermostat housing. The smaller sensor goes to the temp gauge in the dash, and I beleive the other one is a drive pressure sensor. There are 3 small bolts to remove the thermostat housing, 8 mm socket, you can leave the rad hose on, and no gasket is needed, it uses an o-ring type. There should be a new o-ring with your new thermostat, but they are re-usable if in good shape.
Did your stat fail, or do you want a different temperature?

 

deleted09 is right on the money.