Here’s very useful tutorial explaining how to disassemble and upgrade an Asus W3J laptop posted at NotebookReview.com.
If you are going to open up your laptop make sure to work in a static safe environment. If possible, wear ESD wrist strap or at least touch a grounded metal object (desktop chassis for example) before you touch internal laptop components.

Key disassembly and upgrade points:

1. You can easily access one of the memory modules, graphics card, hard drive, heatsink and CPU if you remove one cover from the bottom of the laptop.

2. In order to remove the memory module, carefully spread latches on both sides of the module. The memory module will pop up at 30 degrees angle. Grab the memory module by the sides (do not touch chips) and pull it from the socket.

3. Be careful when removing and installing the graphics card. If you accidentally damage the graphics card connectors, the laptop will not start. In this case you’ll have to replace either the graphics card or the motherboard, it depends on witch connector is damaged.
Handle graphics card by the edges, do not touch chips.

4. You can remove the cooling fan and clean the heatsink. Removing dust will prevent laptop overheating.

5. Do not forget to apply thermal compound on the CPU and VGA chip located on the graphics card. Without thermal compound the laptop will overheat.

6. The second memory module is located under the keyboard. Be careful when you are lifting up the keyboard, it’s still attached to the motherboard.

Troubleshooting tips:

1. If you upgraded laptop memory and now it will not start, make sure the memory module is seated correctly, all the way down into the memory slot. Reseat the memory module and try again.
2. If the laptop works fine for a while and then shuts down without any reason, make sure the cooling fan is connected to the motherboard. If the cooling fan works but the laptop still shuts down it’s possible that you forgot to apply thermal compound on the CPU/VGA chips.
3. If your laptop start but the keyboard doesn’t work, make sure it’s properly connected to the motherboard. Reseat the connection and try again.