Did you actually see the coolant loss/temp gauge spike? Reason I ask is that more than once here a shop has diagnosed engine failure and it's turned out to be something much simpler.
Care to share what it was that failed? There's been a few (very few) threads on replacement motors if you search. Some have had the best lucky sourcing a Tundra/Sequoia motor and swapping over the necessary bits for fit.
Search threads, "engine replacement", titles only, 100 section only.