You can integrate Nav 3D Pro by creating a class that extends the Pathfinder type used by the Behavior Designer Pro add-ons. This class acts as the adapter between the existing tasks and Nav 3D Pro: implement the Pathfinder contract using Nav 3D Pro's movement and pathfinding API.
The movement tasks already use this abstraction, so you can reuse them with your custom Pathfinder implementation. You do not need to recreate the actual movement tasks. Use the existing Pathfinder implementations as a reference for your adapter.
The amount of work depends on how closely Nav 3D Pro's API maps to the Pathfinder contract, including destination requests, path status, arrival detection, and stopping. Without reviewing that API, I can't give a reliable estimate, but the integration work should focus on the Pathfinder implementation.
