So, what's the difference in a birthright and a blessing (Genesis 27:36)? Apparently the birthright included all the rights of the firstborn, and the blessing was comprised of the spiritual and material impartation of the goods that were guaranteed in the birthright.
Looking at it more precisely, the birthright included the rights of 1. being the priest of the family, 2. receiving a double portion of the paternal inheritance, 3. having the judicial authority of one's father and 4. (in this case) possessing a sacred importance in relation to the eventual coming of the Messiah (which seems to have been a significant emphasis of the blessing).
The blessing was therefore an execution and deliverance of the birthright, but it had to have been something more too since Esau clearly saw them as two different things. One thing is apparent, the blessing included providential involvement. So, perhaps some of the cultural understanding of the two things has been lost in history.
Whatever else might be said though, Jacob was definitely guilty of manipulation in obtaining for himself those things which otherwise would have gone to his twin brother. And, it almost cost him his life...
Isaac loved Esau. Rebekah loved Jacob. Isaac sent Esau out to hunt for meat for him to eat during the blessing ceremony. Conniving Rebekah sent Jacob in to trick Isaac into bequeathing the blessing on him rather than on his brother Esau. She was counting on Isaac's handicaps (including blindness) to give her favorite son the edge he needed to deceive Isaac.
Jacob had "scarce gone out" of Isaac’s presence when Esau came in. When one considers just how furious Esau was, it's easy to conclude that God really spared Jacob's life by getting him out of that tent before his brother came in (Genesis 27:41). Truly, God frequently superintends in mercy even when his children are acting selfishly and irresponsibly.