Adding trailer brake controller. Where's the brake wire I tap into?

I'm going to be installing a Prodigy P2 brake controller on my 04 3.4l. Does anyone know where's the wire that I tap into? I looked at the brake pedal and I don't see any wiring or a switch. I haven't taken off the dash piece below the steering wheel yet so I don't know if I was looking in the right spot.

What should I be looking for? Any particular color as I don't want to tap into the positive side.

 

I believe I found my answer in another thread. It looks like I have to remove the panel below the steering wheel, possibly remove the air venting, and tap into the green / white wire located on the brake pedal.

If I'm wrong, somebody please correct me before I screw this up this weekend. Anyone know the size / gauge of wire tap I should use?