You're right, the 2011 automatic also uses WS. It wouldn't hurt to drop the pan and change the filter but you're right, you would need a small torque wrench, a funnel, a drain pan and obviously a socket set. You could probably pick up an inexpensive torque wrench at Harbor Freight.
I don't know how you would stop the flow (once it starts draining out) at one quart, the pan holds approximately 3 quarts (I believe the book says 2.8 quarts). That's also a lot of extra wear and tear on your drain plug and transmission pan threads. Personally I wouldn't do it that way, I...
Even though they flushed it they may not have gotten all of the old fluid out of it. I have a 2012 Corolla that I bought used with 114,000 miles on it to use as my commuter and I have drained and refilled my transmission twice (at each oil change) with Toyota WS fluid since I have owned it and...
David, I've never had the issue but I recommend you check a local salvage yard to see if they have a replacement seat available. You could also perform a google search for the item. Good luck!