1. No.
2.
www.nissanparts.com,
www.4x4parts.com,
www.purenissan.com, there are more, just search for them, man.
3. Modify heavily how? For offroading? For street use? Details, please. There's not much out there for Pathfinders to begin with, a lot of custom fabbing and hand work is generally involved with customizing Pathfinders.