yes, you need to connect all three on the cams hardwire kit. battery , accessory and ground. he is correct that there are seperate wires for this. this will connect your camera not using any of the switches, unless you really want ability to turn it off .pic is from another post in forum.
i say yes to led, lighting is way better. you could do after but just save yourself the trouble. also remember on a sport s, its only headlights and fogs, your fenders will not be led. (i just swapped to led bulbs)
trailer tow yes, just for switches even.
i have v6 non etorque so can't comment...