Yikes! That video gave me anxiety! So tiny and so easy to mess up. With the 400SE only being $150 I think I would just buy a new pair...Found this cool. I wish more repairmen like this were in my area. 400SE Driver Trace Repair
On a sort of related note, I bought a pair of HE-560 V1s shipped from the US to Canada, and upon arrival both drivers were dead I plugged it to various systems in my home hoping that some current would re-energize them, but no dice.
That sucks about your 560! If both side are totally dead it might not be the membrane but rather the wiring going from the jack to the membrane and that would be much easier to fix and someone with decent but basic soldering skills could fix that. I'm assuming you already ruled out the cable?