I need some supporting points on why Pi's story in "Life of Pi" is an example of the Quest pattern (overcomes challenges, etc.).Basically why is...

A traditional "Quest" story involves a hero who must overcome challenges in order to achieve a goal or treasure.  Think of Odysseus from "The Odyssey".  He is a heroic leader who must overcome a series of obstacles in order to get home. 

In this story, Pi fits the characteristics of a hero, even though he is only 16.  He is intelligent and mature beyond his years, as shown by his studies in religion and in science.  He speaks insightfully about his fellow students in religion who were "in the thrall of reason, that fool's gold for the bright."  He shows he is able to integrate spiritual and intellectual concerns in his life, even at his age.  His frienship with Mamaji also shows that he is beyond his years; he does not associate with his peers, but with his superiors.

After he is stranded, the survival skills that he demonstrates also prove his herioc qualities.  Those skills aren't just about living in a precarious situation on the lifeboat, but are also about his ability to mentally cope with his situation and his loneliness.  He is able to accept the deaths of his family, showing his maturity:

"I would be in the direst of dire straits, facing a bleak future, when some small thing, some detail, would transform itself and appear in my mind in a new light."

The obstacles that Pi faces are multi-fold.  He must deal with being stranded on a lifeboat.  He must deal with dangerous and precarious relationships to stay alive on that lifeboat.  He must deal with the death of his family members.  It doesn't matter which version of the survival story is believed in the end - these three main obstacles are still the same.  Finally, Pi must deal with the challenge to his religious faith, as his questions how such a tragedy could happen:

"'Every single thing I value in life has been destroyed. And I am allowed no explanation? I am to suffer hell without any account from heaven?"

The quest that Pi is on - or is thrust into - is the quest to establish identity.  It is significant that Pi is only 16 - he must decide who he will be as an adult.  He must make meaning of life, with all of its obstacles and tragedies.  He must deal with how is values correspond with the society around him, and reconcile the need for survival with the need to uphold those values.  That is his quest, and in the end, he walks away from the Japenese men sure of himself, though leaving them with uncertainty.