First step is to cover the defroster vents with a towel so that you don't loose anything down them.
Next remove the little snap in covers over the screws of the plastic housing that is under the TV. You should be able to carefully pop them out with a very small screw driver inserted in the little notch. With the covers off you can remove all of the screws as well--the plastic housing will still be attached to the wooden faceplate from the inside.
Remove the center sun visor (if you have one).
Remove the center speaker over the top of the TV by popping off the front screen and unscrewing it--disconnect the wiring after noting how it's connected.
You should find a couple of black screws going into the wooden faceframe from inside the cabinets on each side--a bit hard to see but they should be there. It would probably be helpful to have someone support the faceframe while you remove the screws. With the screws removed your should be able to tip out the top of the faceframe and then it and the attached plastic housing should come down and off.
The TV itself is secured by a metal bar across the top held down by a couple of big bolts, one on each side. There also may be adhesive foam underneath the TV as well. Disconnect the various wiring and power cord and then remove the clamp bar. You almost certainly will want another pair of hands to help with actually removing the TV--those Sonys are quite heavy!
Just fyi, here's my old thread over on iRV2.com detailing my front TV upgrade:
Front LCD TV install in 2005 Vectra (Long)