Most of those questions are answered by the documentation in the SDK. Take a look at the ChannelPackagingAndPublishing.pdf.
There is no difference between a private and public channel aside from visibility to the end user and the approval process for publishing.
My Channels: http://roku.permanence.com - Twitter: @TheEndlessDev
Instant Watch Browser (NetflixIWB), Aquarium Screensaver (AQUARIUM), Clever Clocks Screensaver (CLEVERCLOCKS), iTunes Podcasts (ITPC), My Channels (MYCHANNELS)