Thanks! I know the feeling all to well. I checked the diagrams in the Chilton, Haynes, and Toyota manuals. None of them were correct. I didn’t find it by choice, but by necessity.
I was trying to help the neighbor kid learn about proper maintenance and earn a few bucks by changing the engine oil, tranny fluid, and flushing the coolant. Unfortunately the oil and the coolant both came in one gallon jugs. By the time he figured out that he put the oil in the radiator it was too late. We both learned a lot that day. ;-)
The vehicle does need to be jacked up or over a pit to access the drain plug. It’s on the back side of the block about ½ way up and a little to the right of center if I remember correctly. It’s not hard to get to once you find it.
Rather than just doing a simple drain and refill, I’d recommend a chemical flush from the top side. It will clean out any impurities that may have built up over the years. And as always, if you’re not refilling with premixed coolant, make sure you use distilled/deionized water and straight coolant.