Sony or any of the manufactures would never sell or release any technical or service information for their computer products, to anyone who is not authorized by them. Even if you had the service information, there would be very little you can do on your own. It would be impossible to buy most of the parts that they are using on their boards. For troubleshooting, you would need the proper diagnostics setup and tools. You would need the proper solder work station to be able to change the components used on their boards.
The only thing you have a chance to fix on the laptop is an obvious cold solder connection, or if you find a bad capacitor or simple component that you are able to decoder from the board, and solder in a new one.
The authorized service reps for these computers do not have the circuit diagrams for these computers. The only technical information they have is a parts listing, and the procedures of how to change the parts. They do board level and module service only. Other than that, the service will fix a cold solder connection, or do a simple repair only.