Marfy,
Maybe you've already figured it out, but I just installed mine today, and it was way easier than I expected. Granted I do have a V6. My buddy has a 2013 V6 Taco, and he told me where he found the hole for his cartridge block heater--it was the same place that I found mine.
Basically, I reached down to the catalytic converter on the back of the engine on the driver's side and I literally got my hand on the O2 sensor going into the cat as if I were going to try to pull out the O2 sensor. This way, my fingers were curled around that rear part of the sensor, where I could then relax my hand and feel around the engine block in that direct vicinity, just inches away from that O2 sensor, where eventually one of my fingers found a hole that probably an average-sized finger can fit into.
I'll see if I can enter some pictures here next. And by the way, a plug, zip ties, the cartridge, the electrilube stuff all came together from my local Toyota dealer, where I ordered the block heater by simply getting in touch with the parts department. Was maybe $75 total including shipping.
The part that slides into the port. Lube the hole and the port, but not the prongs where the cord will connect.
As you see, the port is right near that rear part of the O2 sensor.
Magnified.
Looking up from below, you can see the prongs of where the cord will plug into the cartridge. You can also, before installation, see the empty hole from down there if you get at just the right angle.
Other notes:
*Prior to installing the unit, test it via a simple wall outlet to ensure functionality.
*Consider sliding the unit into the port with the unit plugged in already. I say this because I had a hard time plugging the cord into the back of the unit with it installed.
