Don't have a washlet yet. However, here's the chart about which washlets work with which toto toilets. http://www.totousa.com/Portals/0/Bro...omp-1009_2.pdf
My understanding is that the Washlet only does stuff when you ask it to. You won't get a shower or konked in the head while throwing up.
Changing the seat should be almost as simple as changing any toilet seat, except you have to turn off the water to the toilet first.