Don't do it. The '06 LX kit is designed for rear controls for the NAV. Your NAV (06 GX) and mine (05 GX) are identical. If you go with the '06 LX kit it won't work. Remember, the kit wasn't designed for your model.
Does the CD changer need to be disconnected to work? I just had my '05 LX kit installed and it doesnt work.