Hygena cooker hood

I need to replace the tubular wire-and-plastic duct which connects a Hygena APP2510 hood to the outside world. Starting at the outside, the duct passes through the roof space, down through the kitchen ceiling and then through a square-section S/S duct: this goes through a high shelf (which conceals the wiring) to the top of the hood itself, about 21″ below the ceiling. The tube seems to go right down to that point, just above the motor. Does anyone know, please, if there is a way of getting at the connection without taking the entire hood off the wall?

‘Vecchiocontadino’