You should have just got through the Weapons Factory, and headed up an elevator. This elevator will take you outside. When you step outside, a cut-scene will play. In this cut-scene, Krew will come into the scene. He will talk about his love of weapons, and his favourite, Precursor Orb. He will talk about how he is planning to blow up the stone. Jak will take on Krew, even though Krew has just given him a gun upgrade.
Head into battle, and Krew will originally set some clones onto you. These clones will not be too much of a problem, simply take them out with your Scatter Gun. The best way to do this is to run in a circle around the platform, shooting any ones that you see. Once they are all gone, Krew will come into the battle. Use your Vulcan Fury and keep hitting him so that he can’t hurt you. Be warned, you will probably hit him off the edge, and when you do, make sure you do not jump off the edge when tapping forward to aim at him. Once you get rid of a third of Krew’s health, he will send his clones back onto you. Do the same thing again, and you will eventually be able to fight Krew again. The clones will be a bit harder to destroy this time.
Fight Krew again and use the same technique to drain another one of his health bars. You will now have to take out more clones. The third time you take on Krew, he will not stop using the clones. Concentrate on Krew, but also make sure you do not run out of health from the clones that are running at you electrocuting you. With enough luck, you will be able to drain Krew’s health to absolutely nothing. Afterwards, a cut-scene will play, and Krew will destroy his weapon. Ashelin will save Jak and Daxter, and drop them off in the city.
You will now have defeated Krew, and will also have access to his Salon now. Go to his salon, which will be an icon on the map. Tess will be there, and she will talk about the thing in the machine, and you will have to beat the Metal Head Mash Game. To do this, hit the normal and gold Metal Heads. Avoid the red ones as they will decrease your score. Once you get a high enough score, you will retrieve a Time Map from the machine. You have now completed this mission.