Answer 1: Simply talk to Canderous enough times, ask him about his past, and so on. The quest should eventually be triggered. And no, I don't recall anything about Canderous' and Juhani's sidequests being related.
Answer 2: I'm not sure what you mean by this question.
Answer 3: To be frank, I don't think it's worth it to take yourself to Manaan in the first place. But since you have to go there eventually, then yes. Bastila is arguably among the three most powerful party members available, so having her escort you around could be mandatory, depending on the difficulty level.
"Grant Allen [...] had written a book about the Evolution of the Idea of God. [...] it would be much more interesting if God wrote a book about the evolution of the idea of Grant Allen." ~ G. K. Chesterton, The Everlasting Man
Last edited by TKA-001; 04-08-2008 at 06:53 PM.