Richard Alpert takes Ben to the temple to be healed

As Sawyer and Kat with Ben are being marched through the jungle, Richard Alpert appears. Sawyer asks him "Where the hell'd you come from" and Richard just brushes it off. Richard looks a Ben and asks "Is that Benjamin Linus?" Sawyer replies "You two know each other?" Richard asks what happened and Kate tells him that he was shot. Kate asks Richard to save Ben's life and she asks "Can you?" Richard says that if he takes Ben, he'll never be the same again. Kate asks him what he means and Richard says that he'll forget this ever happened and his innocence will be gone. He adds "He will always be one of us." He asks "Do you still want me to take him?" and Kate says yes. Richard takes Ben and then Erik steps up and tells him that "you shouldn't do this without talking to Ellie and if Charles finds out..." Richard interrupts and says "Let them find out. I don't answer to either of them." he then walks off with Ben into the jungle.

Richard carries Ben all the way to the temple where he backs in through a doorway.

So what happens to Ben in the temple? How is he healed? Why does he forget what happened and lose his innocence? How exactly does what's in the temple change him?