I've had better luck emailing Kindle support, but only for specific issues.
For the kind of questions you were asking,, you should have just come here (where the folks who REALLY know stuff hang out) or to any number of excellent Kindle blogs that have technical advice, such as the "tech tips" that appear in each post on Len Edgerly's
Kindle Chronicles.
Of course you can transfer material, including books and documents, to your Kindle as long as it is in a format the Kindle can read. I personally find emailing easier, but USB works fine, just remember it has to go in the "documents" folder on the Kindle.