Here's my old thread on that may have some helpful info:
Front LCD TV install in 2005 Vectra (Long)
You need to remove all of the screws holding the plastic pan under the TV (screws accessible after popping off little covers over each one)--also a good idea to cover defroster vents with a towel so you don't lose anything down the vents. The lip of the plastic will probably still be attached to the wooden faceframe with some screws from inside that aren't accessible until the whole thing is down.
You also need to remove the center sunscreen if you have one.
If you have a small speaker above the top of the TV that needs to be removed as well. Pop off the grill and then there are a few screws to remove the speaker (make note of the wiring connections before removing them).
The wooden faceframe is held in with a couple of screws into each side through the inside wall of the adjoining cabinets. They're black on black, so you may need a light to see them. Once those are removed the whole faceframe and attached plastic pan should tip out a bit at the top an then come down and off.
The TV itself is held down with a bar across the top secured with a large bolt on either side. There's also probably some sticky foam under the TV holding it in place as well. The tube TV is QUITE heavy--I would recommend having someone else available to help lift it down (after unpluging the power and wiring from the backside).