The previous owner had removed the rear sunshade upper bracket and guide tube in order to fit a cellphone antenna. I was luckily able to find replacement parts cheaply and bought a new guide rope to reinstall the sunshade.
I threaded the rope through the tube, and then installed the tube. Had someone press the switch and I turned the rope until it got pulled in by the motor. Removed the tube, lubed things up a bit, installed the tube again, the little spring and then fit the upper bracket.