update!! i have not done this, but heres another option:
instead of tapping into your stock harness, you could theoritacly rearange the wires...
look at your stock radio harness (from behind) from this pic use a needle of some sort and poke right under each wire to be able to pull out the wire, and just rearange the wires so that the right looks like the left side, i have not done this but i just though of it, as far as the little one on the top left, you still need to solder 2 wires to it:
