In plain words
Expect two visits. On the first, the technician makes the door safe to use or safe to leave closed, identifies the manufacturer and model, measures the section, photographs the damage and its neighbours, and checks the hinges, rollers, tracks, cables and springs for anything the impact disturbed. The replacement section is then ordered to that specification, since sections are made to order for each model rather than kept on a shelf. On the second visit the section is installed, the hardware is refitted, the springs are re-tensioned if needed, and the door and opener are tested through full cycles before the technician leaves.