I took a peek at the codes for Joplin and did not see anything saying you could not OC. I am not sure about carrying on your person while in your car, I know in Boone county where I live I am not able to carry on my person in the car unless I have a CCW. Might want to get in contact with someone who could answer that one for you.
Bit off topic, but mind if I ask what your MOS is? I was 11B myself, Arkansas Guard.