I am not at all sure about what you were told by Toyota. Far too many people ignore changing/flushing the transmission fluid. The same is true for most if not all other makes as well.
What I don't know is this stuff about the difficulty and the requirement to pull the transmission to do the work. I am sure someone will be here soon to let you know.
BTW don't believe the story about how changing the fluid will cause the transmission to fail. That story is common because the transmission does often fail shortly after having the fluid changed. However the reason for the failure is the fact that the fluid had not been changed as soon as it should have been (something like 40 - 50,000 miles). When the transmission starts to feel wrong or show signs of a problem, then they have it changed. When that happens people like to blame the car or transmission rather than themselves for failing to change it. I really feel sorry for the poor guy who has done everything he knew should be done, but no one told him to change it or someone told him that changing it would cause the problem.