I don't think a diagram is needed.
After you remove the back of the TV you should see two wires going to each TV speaker. Each external speaker would connect the same as the internal ones. You could just disconnect the internal speakers and extend the wires through a hold in the back of the TV to your speakers. You could install speaker terminals or a headphone jack on the back of the TV. It's mostly a matter of the layout of the TV where and how you do it.
A switch could be installed to chose whether you use the internal or external speakers.
You would use passive speakers that could be driven by the TV amps or connect a speaker to line level converter than would let you use active speakers.