Is it the flex you want to fix, or the rewind?
if it is the rewind, I would assume not doing it, could be the spring, or spring lock point, you would need to take it apart to find out, if its the flex, you will need to take the unit apart, to remove old one and fit new one
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix vacuum cleaners.