Riding level and cost haven't been announced. What's confirmed is a Burning Crusade-style model: the mount comes with the riding skill instead of being bought separately.
An appraiser's rule: read the stats, not the label.
The new ship routes come from the BlizzCon panel recap; exact docks may shift before launch.
The bear tanks and does most of the damage; the hunter supports from range. This is the consensus leveling build through level 30.
Pets scale with the hunter's stats, Agility included, so gearing up strengthens the bear. Aimed Shot is baseline and shares a cooldown with Multi-Shot.
Builds for 40 to 60 exist online, but their own authors call them theorycraft. Nothing past 30 has been played yet.