Thank you @scribe for the excellent advice. I followed it and was successful in fixing the power button. Also agree that GregL's take apart video was extremely helpful. I have a couple of follow on comments.
* there are 2 tabs on each side of the Kindles back cover, they appear to operate by pressing in the tabs, but I didn't know this and broke the tabs. However there are also 4 hook-like tabs around the battery shield, as well as glue, that also hold the back cover in place, so don't stress if you break a side tab.
* the 2 tabs at top and bottom of Kindle back cover are pretty long, so I second the advice of undoing the side tabs first, freeing the center from glue and hooks, then bending or curving the back cover to be Able to slide the top or bottom tabs free.
* be Careful flipping the ribbon cable connectors up before sliding the ribbon cables out. They are delicate and don't all operate the same way. I damaged one ribbon cable on the side by gripping it with tweezers when I did not need to, and disabled two of my page turn buttons. (Now, for my next trick...)
* I did not need to remove the battery to fix the power switch. I also did not need to remove the entire front bezel, just pried the bottom half up.
* second the advice on the motherboard. It's hard to remove and fiddly to get back in place. It may help to peel off some of the glue sheet so it doesn't bunch up during reassembly. And if the power switch has completely dislodged itself, like mine did, it will escape without you noticing.
* use the points of tweezers to carefully put tiny amount of glue into holes on motherboard. Let dry before soldering.
* glue everywhere is quite strong, responds well to the slow, patient, pry apart gently method.
* Im not sure where the 1x4 mm fibrous bit fits into the picture; clarification would be good.