Step 3: The Transmitter
Open the battery compartment, remove the two screws holding it in and pull it out carefully.
Next, remove all the battery terminals from the plastic, they should slide up out of the slots they're in. (Mine came out easy after applying some heat to them with the soldering iron).
Once you have that done, Unsolder the wire from the negative terminal and desolder the diode from the positive terminal.(Be sure to keep the diode attached to the positive wire.)
Replace the battery box and begin cutting out a slot for the usb.
You will have to cut part of the battery case and the outer case of the transmitter and it helps to have the battery box in while doing this. (Pictures)