I just did mine a couple days ago. It was a bit of a challenge for me to reach back there to do the work.
The rear had a small crack at the top that leaked coolant down the back of the engine and transmission.
Picked up the part at the dealership for $115 (Heater manifold LR109402 for V8 and LR109401 for V6).
Seemed fairly straight forward after studying pictures of the engine.
Here's a quick sketch.
I removed the intake manifold as I was going to replace the front crossover pipe as well.
-Disconnect the small coolant hose at the top that connects to the intake.
-Unscrew the 4 screw. Some are visible. Others you'll have to do it by feeling around.
-Unplug the sensor and remove the two wire loom ties/holder. I had to break them off as I was not able pry off.
-Remove heater hose connector. I struggled for a while to unclip it from the back, then realized that it was easier to unclip further up the hose (past the bleeder screw).
That's it! Just reassemble and zip tie the wires back in place.
As a side note. My new front crossover pipe did not come with a bleeder cap (LR011038 green on image).
When i tried removing the old one, it just fell apart. Need to make another run to the dealership...