Assuming that turning VSC off on your 06 GS300 is done the same way as on the current US spec GS350, look at page 25 of the attachment. It looks like the current VSC/Trac is a bit more sophisticated than mine in that Trac and VSC can be turned off independently.
You'll probably want to read your owners manual thoroughly -- you car there is a LOT of features.
Just checked out the pdf, but my gs300 doesn't have the button for VSC off, there is only button located near there which is sport and snow. :S
I"m assuming VSC is always on when I start the car, unless if it's off then it should show up on the dash no?