Wow I just did this 2 hours ago and boy is it fun!!!
1st off they dont have a true in dash kit yet so I had to use one for import cars... works but I had to remove the slide down scion cover off to make everything fit. ok now to the removal.
1) you need to take off your shifter knob.
2) remove the shifter cover being carful not to pull to hard and fast and gank the lighter wires in back.. they remove easy though.
3) then you have to grit down and reach under the clock where the cubby hole is to store stuf with your palm up and just push up and pull out. It feels as if it wont come out but it will. Becareful again not to yank the control wires out.
4) then youll see 4 bolts holding the radio on place in the bracket it sits in. Remove these and you can get to the radio itself. Unplug the wires in back of the radio and you got it!
Note: If you goto install a custom deck, you have to remove the slide scion cover or it wont fit all back together. Unless someone found out how, I couldnt do it and I tried all different ways for about 45 min.
Hope this helps.. Oh all standard toyota harnesses work for the new head unit.