Instructions
Purchase a new Blu Ray drive. The drive houses the laser. Blu Ray drives can be purchased online or can be repurposed from other devices supporting a Blu Ray drive such as laptops and Blu Ray players, or even another PS3.
Expose the PlayStation's internal drive by removing the top casing. The casing clips on so just remove it by pulling up.
Unplug the Blu Ray drive from the rest of the system. The drive can be identified by the slot opening for a disc at its front. The plugs connecting it to the rest of the system are white and exposed at the top right of the drive.
Disconnect the data cable at the bottom of the drive. It is taped to the drive by blue tape. The cable is delicate so be cautious.
Unscrew the screws on the Blu Ray drive casing now that it is fully removed from the rest of the system.
Separate the drive's casing from the body, unscrew the screws on the next level of casing and open the drive to expose the Blu Ray laser.
Remove the screws connecting the laser to the rest of the drive. With the laser loose remove it and replace it with the working laser.
Re-affix the screws and casings in reverse order and re-install the drive into the PS3 to restore the system to its original working state.