Pulling Nav Unit from Lexus GS to get access to the back of the nav
You will need a small flat head screw driver, a phillip head screw driver, a 10mm socket and a towel to protect the navigation unit.
First, remove the plastic trim underneath the nav( just right above the ashtray) by pry it out with a small flat head screw driver.
Hint: Tape the screw driver with Scotch tape to protect the finish of the trim.
Second, put the shifter into "D" position. DO NOT START THE CAR. Just press the start buttom twice( foot of brake pedal at this time) and put the shifter to " D" or you can remove the shift lock tab and press the buttom, so you can move the shifter to " D"
Unscrew the shifter and pry up on the center console.
Third, remove the phillip head screw on each side of the side cover and the pry out.
Gently remove both covers.
After that you will see 4 10mm bolts( 2 on each side). Remove those bolts from the nav screen bracket and remove the nav unit.
If you look under the nav unit you will find a piece of metal bracket on each side to grab onto and pull it out. Do not pry on the side of the Nav unit or try to remove the AC vent.
One more.
Oh, the AC vent is part of the dash. If you attemt ot remove it... 
you will have yourself a new dash.
