Step 4: Reassemble and test
Replace all the screws in the circuit board. Put the face plate sticker back on. Put the battery tray back in. You're done!
Now your remote control should still function as an IR remote control. Test it and make sure. Don't forget to set your NEX drive mode to "Remote Control". It's under Camera -> Drive Mode.
Now plug the 3/32" male to 1/8" female adapter into the new jack on the remote control. Plug the IR emitter cable (and optionally a 1/8" stereo extension cable) into the adapter on the remote control. Stick the IR emitter over the receiver on the front of the camera. You should now have a working wired remote which does not require line of sight between you and the front of the camera.
See the attached photo for the complete setup.