The micro USB port was no longer accepting electricity to charge the battery. The port itself can not be removed from the motherboard without breaking solder.
Replacing the motherboard was the easiest thing I've ever done on an electronic device. Once the case was opened, all that was required was disconnecting the six or seven peripherals, lifting the board out and setting the new one in place. A couple points to consider is that the lower right corner has a portion that must go under a piece of plastic on the case, the battery connection is very stiff and does not need to come off very far, and the connector for the IR sensor on the side is a different type of connector, which must be unlocked first by prying the back side of the board connection up before removing the flat cable.
The plastic used in these things is really quite soft, so don't use anything metal to either open the case or disconnect any cables. An opening tool from ifixit is what I used and it worked great, but I've seen other tools as well from a guitar pick to a folded piece of a plastic pop bottle. (Sorry "soda" bottle for the yanks.)