First of all have you checked to see if the wireless adapter is showing up in the Device Manager in Windows Control Panel. If it is there but has a yellow exclamation mark then it is possible the driver is corrupted. Uninstall it and let reboot and let Windows automatically reinstall the driver.
To answer your question:
Yes it can be replaced and is not soldered to the motherboard. Gently pry off the black antenna connecting wire, unscrew mounting screw and slide card out of socket.
Here are the disassemble instructions:
[guide|126712]
The wireless card in circled in red in the first photo.