What is the process under Missouri personal injury laws for filing a claim against other driver's insurance

What is the name of your state (only U.S. law)? Missouri

I was in an accident in June 2007 where the girl i was riding with lost control of her car and flipped it onto its back. My foot was crushed under the dashboard--4 bones were broken and all of my soft tissue was "blasted apart", as the doctors said. They called it a "Liz Franc" injury, which I think meant that my main ligament or tendon was ruptured as well. I spent about 4 months on crutches, and another 2-3 months in physical therapy. I was out of work for 6 months, then tried got a job as a waitress, but had to quit after 2 months because it hurt too bad to be on my feet. I had one surgery about a month after the accident where they put 4 screws in my foot, and then had surgery in March to take them out. After the 2nd surgery, I was out of work for another 2 months. The pain and suffering was tremendous and my foot still has pain..I am also expected to have arthritis when I get older. I am only 19 years old, so this has affected the rest of my life.

My question is--what is the best way to go about filing the claim with the other girl's insurance company? About how much money can I expect and will I get more if I file the claim myself, and get ALL of the settlement or hire a lawyer and possibly make more money but only get SOME of the settlement?