j92devils

I'm considering buying this stereo to replace the stock one in my '96 ES300: http://www.crutchfield.com/p_130P4100UB/Pi...UB.html?tp=5684. Will this work since it has a built-in AMP? Do I need to uninstall the factory amp? Do I need something called 'preamp outputs'? Do I need a wire harness?

I pulled my '96 ES300 Car Stereo and it is a KEX-M8346ZT, also a 86120-33021 and I'm looking for a manual for this. Does anyone have one? Or at least a diagram of all of the connections that it has?

Is is possible to install an after-market navigation system in a 1996 ES300? Can anybody direct me to a place where I may be able to learn about this?