You will get faster and learn a lot about why you do certain things to improve running fitness. I have tinkered with running for a few years, but since I am taking it seriously, I got a serious coach. Karen has helped me hit new Personal Bests at an older age and we have only just recently started!
I can't recommend Karen enough as a running coach. She created a training plan for me to not only attain a 5 minute PR in the marathon but she also taught me how to be a better runner and the why behind the workouts I was doing. That has helped me as I continue to progress with my running career.