Try
www.hometheaterspot.com for more info than you will ever need about your TV. They will have instructions on how to adjust your geometry.
Your TV does 1080i and 480p. 480i is upconverted to 480p and 720p is downconverted to 1080i.
Buying a prog scan DVD player has a big advantage over letting the TV upconvert to progressive. The DVD player converts to progressive using tags inbeded in the DVD's data stream and the TV does a "best guess" on the analog signal that is fed to it.
-Robert