I've had my very first fender bender and I believe they're trying to overcharge me?

I was pulling into work the other morning and just happened to catch my bumper on an employees back door of her mom's ford fusion. 2016 model I believe. I had a lapse in my insurance but is back on now, I've only got liability so I'm not sure if they will help at all or not. But she told me today that I would have to replace her door for $1700. That sounds ridiculous to me. There's all debt maybe the size of a grapefruit and a few scratches. The door opens and closes fine, we even checked the inside panel and it was in prestine condition. Can they not have the dent popped out and the scratches painted over? Why would I have to replace the whole door? What will happen if i refuse to replace it, due to mainly I can't afford it. It would take me months to pay it off. Can they be told to have an estimate from somewhere else, other than the dealership? I really need help. Thanks!

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