What repair can be done on this wingtip? (777)
What action need to be taken towards this kind of damage?


The aircraft will be grounded immediately and damage like this needs to be repaired in a timely fashion to get the plane back in the air and making money once again. Its worth noting as well (under FAA regulations) that you would also be in breach of § 23.1385 Position light system installation as the position lights are usually installed in the wing tip. 

For damage like this Boeings AOG team will be brought in to repair it


  The Boeing team isn’t called in for everything. Airlines have
  incidents every day, Testin says, and most airport ground crews can
  handle routine repairs—a window cracked by a bird, a component failing
  calibration. An AOG intervention is required for the big things: an
  airplane off the end of a runway, landing gear accidentally retracted,
  a flaming tail drag, two 150-ton behemoths kissing wingtips on the
  ramp.


Since it's Boeing themselves coming in, they may use a variety of reference material to fix the damage and it really will vary case by case depending on what needs to be replaced. In this case the damaged metal will be removed until they get to an area at which they can begin to joint on a new wing tip. 

I cant find any great examples of wing repair being done on jumbos as its most likely done behind closed doors but here is a great video of it being done to a small aircraft generally speaking the fundamentals are the same as the designs only change in size. Remove the damaged skin, get the wing down to the ribs/spars, repair/replace ribs if necessary, re-skin wing.