To be certain, you should:
* Consult your vehicle's repair manual: This will have a diagram showing the exact location.
* Use an online parts diagram: Many auto parts websites allow you to enter your vehicle's year, make, and model to view diagrams showing the thermostat location.
Without knowing the specific year and engine of your Chrysler 300, a more precise answer isn't possible. Be aware that accessing the thermostat may require removing other parts, so if you're not comfortable working on your car yourself, taking it to a mechanic is recommended.