The video is for a different blind, on yours you would need to remove the pin possibly destroying it. Why are you attempting such a pointless task? Continuous chains are not longer used due to the choking hazard it presents. Replacement gears are widely available but again for use with safety...
Maybe cut out a small section of facia which will give access to both wall and soffit after which replacing is just a case of replacing facia with a couple of joint covers.
Alternatively install a soffit vent which gives a better view and aids cable install, I used one for my cctv cable install...