It really depends on what USB port. The USB port on the right is attached to your Logic Board and as Mayer said, it is not a DIY fix to replace just that USB Port. Replacing the Logic Board itself also requires a good bit of technical know how and confidence. You will need to disconnect and remove your Optical drive, both fans, 3 heat sensors, and a few other connections from the Logic Board. You will also have about 9 T6 screws to remove before you can lift it out. You will need to ensure an anti static working surface.
Now, if you're talking about repairing just the USB port... that is going to require soldering skills. Or you can now just replace the Logic Board.
As for the USB Port on the left, that is connected to the DC I/0 MagSafe board. It is runs under the AirPort card and you must remove the left fan and Airport card to get to it. You will also need to disconnect about 5 different plugs, at least 2 from the Logic Board.