How does Enkidu change Gilgamesh? Challenging the king to combat, as Enkidu does, was a deadly offense. Does the text ever clearly state why or how they go from enemies to friends?

After Enkidu's challenge and subsequent loss to Gilgamesh, the two become friends. There is mutual respect between the two. Enkidu's challenge was a great offense, something punishable by death, but I think Gilgamesh enjoyed it.... he enjoyed a victory against this worthy opponent, particulary because it enforced his reputation among his people. A result of their fight, Gilgamesh is visibly changed.... he not only views Enkidu as a worthy opponent, but someone who is a worthy companion as well.