In an accident, advice dealing with other ins company

My sons Duster was hit by our neighbors daughter backing out of their driveway. Her dad immediately phoned their insurance company and took responsibility for the accident. Geico called me within 20 minutes and told me they were taking responsibility for fixing my son's car. I have an appointment to take the car to one of there facility's for an estimate and don't know what to expect. I plan on using a repair shop of my own choosing. Should I have my estimates in hand when I meet the Geico rep? How do they get prices for parts on these old cars? Any tips for a anxious dad?

FB_IMG_1491784596185.jpg

FB_IMG_1491784581646.jpg