Hamlet- To Avenge or Not to Avenge?

When Hamlet speaks to the apparition at the end of Act I, he discovers that this ghost is his deceased father, Hamlet. In fact, Hamlet's father was murdered by Claudius, the current King. The ghosts says, "Upon my secure hour thy uncle stole / With juice of cursed hebona in a vial / And in the porches of my ears did pour" (I iv 68-70). The ghost then commands his son to avenge his death in order to restore the Kingdom. He does not want the land to become, "A couch for luxury and damned incest" (I iv 90). To do this, Hamlet must kill the King and assume the throne. 

Hamlet, unfortunately, is caught in a dilemma. If he kills his uncle, Claudius, he becomes a killer, whether or not if it's his wish. The other option is to disobey his father's will, and let the murderer Claudius rule the Kingdom. With a steady conscience and hopes of pleasing everyone, which of these routes will Hamlet choose?