Remove the old mirror. This is a FIVE SECOND step! Install a small flathead screwdriver about an inch into that tab, and pry the tip of the screwdriver away from the glass. With pressure on the tip, the mirror will slide up off of the mirror mount. The Donnelly mirror will fit on the stock mount, so if your mirror came with a "mounting kit", you shouldn't need it(unless your RAV is different than mine).
Run your wires. This requires you to remove some trim pieces. Don't let your wife see you do this or else she'll for sure divorce you.
You need to take off the light diffuser(the plastic piece where the light is). Get your handy dandy small screwdriver, and pry away where the 4 visible tabs are.
Under the plastic diffuser, you'll find a bastard screw to remove. There will be 3 phillips screws to remove.
Now you can remove that bastard console thingy. Pop out the the side closest to the windshield first, and then slide the whole piece downward toward the windshield. There are guiding clips that hold the piece on the headline. All this so you can fish the wires to the mirror.
A little theology lesson: You can run the wires on the left side, or the right side. I chose the driver side for no apparent reason. Actually, I'm familiar with under my dash, and there's more room to get my fat hands under where the steering wheel is, than where the glove box is. Therefore and thusly, I removed the drivers side shade flap thingy. 2 self-explanitory screws.
Remove the door molding around the pilar area. It pulls right off, and you only need to remove the part touching the plastic panel.
Now remove that plastic pilar panel. I believe there's 2 metal clips holding it in. It pulls off pretty easily, and it's flexible enough to not feel like breaking if you have to pull it hard.
Hook up power wires.
Very simple step that doesn't really require pictures. There's a plug that goes into the back of the mirror. You can very easily tuck it under the roof where the top center console was removed, and then guide it across to the pilar and down under the dash. Its easiest to tap in to the same power source as the radio, and if you need help getting to the wires, here's 
. Now for options... which wire to snip! Since I'm familiar with my stereo, I tapped into the Accessory wire connecting to my stereo.
Use of a multi-meter would help here... If you removed your head unit and see the wire harnesses, find the wire that gives 12V when your car key is turned to "Accessory". Connect the red power wire of the Donnelly to this wire and connect the black ground wire to a good ground. At this point you can turn your key on to see if it the mirror lights up. If it doesn't, you picked the wrong wire. You have failed high school electronics! It should light up beautifully, and if it does, splice into this wire by any means you know how.
Run cables thru firewall into engine compartment to mount sensor. The trick here is to find a way to get the wire from inside the car to the engine compartment. High above where the passengers feet are you can reach the firewall. On the other side of that firewall should be where your battery is mounted. If you look deep down the drivers side of the battery behind it, you'll see a big grommet where other fun things are shoved thru. In the picture below, you'll see red wire loom there, since I used that same hole to run wires for my other 12V junk. That is the hole you run the Donnelly sensor wire thru. There's enough room.. that thing stretches like it's giving birth. Just shove the sensor wire thru that hole, and mount the sensor anywhere you see fit. I put mine in front of the radiator.
Dude... you're DONE! Just pop back whatever panels and junk you took off, and you're good to go!
if you have any questions. Happy RAV'n!