Can't help with soldering but....Go onto eBay and type in 'ipod classic Bluetooth' They will have transmitters and adapters, little pieces that plug into the charging port, that will allow you to use your iPod with Bluetooth. It would be a lot easier than soldering a chip in. Hope this helps!
This probably means that the disk scan was not able to recover the hard disk data. It could also mean a corrupted drive. The bet thing to do is read the link, but if you think it's worth the time and money, then you can take it to Genius. Here's what Apple says to do; http://support.apple.com/kb/TS1373
Yes... you could theoreticially, just remember the iPod may not function as well with the hard drive that it was not designed to carry. This is all I know on this topic so far, so if I were you, I would do a lot of research.
Yes, it can. There is a tiny spring on the power button (the volume and power button are all one piece, meaning you'll have to replace both) that is possibly broken. I would try to replace the on/off/volume buttons, and see if that solves the problem. As for parts, at last checked, I have found the buttons part listed for $4. Just go onto eBay and type in iPod 6th generation nano power button with tools. You will have to reuse the button pieces themselves, though. All they give you is the part itself. From my research, I would conclude that it would cost $5-$20, though I wouldn't recommend anything shipping from Hong Kong or the Philippines, just for quality and shipping reasons. Don't forget to find a guide online of how to replace it. Hope this helps!