Though this isn't the most popular car owned on this forum, but here is a guide to remove & replace the OEM radio in a Toyota Highlander. Note that this radio is just a regular 3-in-1 with single CD, not 6-disc CD changer, so the plugs on the back of the headunit will be different.
Original radio:
Pry out dash bezel from the bottom and work around, dash bezel removed:
Dash bezel:
Remove six 10mm bolts, 3 on each side:
Tilt entire dash forward:
Remove harnesses on radio & climate control:
Dash removed:
Remove eight 8mm/Philips (4 each side) screws from brackets:
Remove 4 more Phillips screws for the brackets:
Dash kit:
Follow the instructions in the dash kit, and putting the dash back in is just the opposite of removal.
Here is the final result:
This particular CD/MP3 player is from Panasonic,
CQ-HX1083U, with a detachable touch screen faceplate that weighs a ton. But it is pretty colorful (if you like that), and comes with 3 sets of preouts, 1 set of CD input, 1 set of AUX input, Sirius satellite radio ready, and wireless remote.