Electronic brake control

Hi all, I just purchased a new 06 Trailblazer Ls, and I would like to intall my electronic brake control. Can anyone tell me if the underdash is prewired for the brake control, or do I need to splice into the brake light switch, as I did with my 97 Astro I traded in?
Second question, has anyone removed the manual mirrors and replaced with the power mirrors? If so what can I expect to pay for this mod?

Thanks in advance
Jim

The wires are just hanging on the left side walll under the dash on the drivers side... mine were wrapped all up in electrical tape and then zipped tied and rolled up to another wire. They did have a little white tag hanging on them with that listed the different colors and what they were though.

Wire Colors are as follows:

Vehicle ************* Brake Controller

ORANGE ----- 12 VOLT+ --------- BLACK
BLACK ----- GROUND ----------- WHITE
LT. BLUE ----- BRK. SWITCH ----- RED
DRK. BLUE ---- TRAILER BRK. ----- BLUE

Thanks for the info.

Jim