HERITAGE DAILY: Guide to the classics: the Epic of Gilgamesh. (Louise Pryke). This is a nice summary of the story of Gilgamesh in the Epic, other related stories about Gilgamesh, and a brief account of the importance of the Gilgamesh traditions, the history of the rediscovery of Gilgamesh, and the current state of our knowledge of the text of the Epic.
One detail: my understanding of the Epic (and I did read much of it in Akkadian with William Moran, many years ago) is that Gilgamesh received the secret of extended life, not eternal life. Utnapishtim (or whatever they think the correct form of the name is now) gave him a plant that would make him young again, but there is no indication that the youth would be permanent. In any case, Gilgamesh carelessly lost the plant, so we will never know.
Regular readers will be aware that Gilgamesh is a character in ancient Jewish literature. He appears as one of the giants in the Book of Giants.
I have collected many past posts on Gilgamesh here. There you can read about him in the Book of Giants, and even in a later Syriac text, and also about most of the other issues mentioned above. And I have some additional posts involving Gilgamesh here, here, here, and here.