The letterbox is NOT at the posted coordinates.
However, it's a good place to park and begin your journey. Your walk will take you on a wide path with some overgrowth. There is a washout to cross over and water maybe flowing (sturdy stepping stones are provided).
But first, you must solve the jigsaw puzzle to find the required projection from the posted coordinates. The stamp inside the cache is NOT a trade item. The letterbox stamp is part of the cache so should not be removed.
Enjoy and have fun! Puzzle begins here.
You can validate your puzzle solution with certitude.