DBAN has you covered, unless you're using an SSD in which case you want to use the inbuilt secure erase using PartedMagic. It's a few bucks, or just torrent the ISO and verify the checksum.
https://Duckduckgo.com doesn't pass on or save any of your search information. The results aren't quite as good as Google's but they're good enough in the majority of cases. As with all good search engines, the more people use it, the better the results get.
Stopping Facebook is as easy as blocking it in noscript and not having an account.