The manual is downloadable, and available here:
As far as 60Hz input signals, there are no 120Hz sources available. The 120Hz is the processing done inside the television itself. Blu-Ray, Xbox, PS3, upconverting DVD players and cable/sat boxes all have a maximum output of 60Hz.
The Information Bar on the television itself will tell you what the incoming signal is. It will always show a 120hz picture because it will convert whatever signal it receives to 120Hz.
Hope that helps!
My father just purchased an 850 series ToC and unfortunatly has misplaced the manual. I have purchased a bd-p2550 player for him and i am having trouble switching the Tv from 60Hz to 120Hz. I have gone through the preset entertainment menu as well as set up auto motion plus in picture menu from low to high. I am running an HDMI monster cable with 6 gbps and 12 bit color. Im still getting only 60 Hz. Any info would be greatly appreciated!