Check the climate controls, make sure all the levels work, including recirc, especially with dual zones. Those blend door actuators sometimes break. I've never broken one but I had recirc stuck once. I thought it broke but I took it apart and all was well, just jammed.
If it has dual zone with the glass sensor dome on the top of the dash at the base of the windshield, you can replace the light switch assembly with one with auto head lights if it doesn't have it already. 300C's had it but not the Magnum on any trim.
And check or ask when the front suspension tension struts were last replaced. The do tend to eat them.
If it has the steering control buttons, you can press and hold both the music and compass button at the same time for 5 seconds or so to get digital readouts you can scroll through in the cluster such as a digital speedometer, pedal pressure, oil pressure, coolant temperature, and more.
There is a plastic parking shift interlock with a spring hook that could break and leave the car stuck in park. More than likely it's already been replaced with a better one or billet one. I just drilled a hole over the broken clip and inserted a cotter pin where the eye serves as the new spring hook.