gmw4

My charging port door on my 2016 Cmax Energi broke in the open position a few weeks ago (see attached photo of my muddy car). When I took it in today for the transmission bushing recall, I asked for an estimate for this repair, and they quoted me over $600*! I said the part is about $100 online, so how is it so expensive? They claimed I needed the entire port door replaced, and painted to match--but the door is fine, it's just that the plastic rod that holds it in place broke off from the housing. Is part 10370 all I need? Do you have to disconnect the battery to replace it? (*actually first they quoted me over $1600, but I said that can't possibly be right for a tiny piece of plastic, and when I asked to review the parts list, it was most definitely not right)