Running a 5K is a great distance to set your sites on improving your fitness, and setting a goal. The training involved does not require the great distances of a marathon.
Develop a GamePlan that keeps you on track to reach your goal. Improving your running economy with specific regimen of V02 workouts will increase your performance, taking seconds, if not minutes off your time. Above all, listen to your body, implement recovery sessions of stretching during the week, and also strength train two times a week. This will help prevent injuries.