BizTalk learning, demand and the required knowledge

I am very new to BizTalk. I need to start working on a BizTalk project.
Kindly let me,
(1) Is it easy to learn or difficult or moderate?
(2) What about the scope/demand in market for BizTalk experience?
(3) How much time it might take for a .Net candidate to learn BizTalk and what I need to know before learning BizTalk?