Sealed transmission essentially means that the transmission does not have a dipstick. The U660E transmission fitted to the Toyota Aurion has a 24mm fill bolt and a drain bolt with a 6mm hex key. Your vehicle is more than 10 years old and has travelled more than 100,000 miles [160,000 KMs]. If you want the transmission to last, then replacement of the ATF is recommended.
For your specific vehicle, based upon my DIY experience and lots of internet research since 2016, I would be just doing a pan drain and fill. At this stage, Definitely NOT a transmission flush to replace all of the fluid. Easiest method involves an accurate measurement of the drained ATF [at ambient/room temperature] and replacement with an equivalent amount. Repeat the pan drain and fill annually for the next 3 years.
Following link to other threads in this Forum will give you more information about replacing the ATF for the U660E transmission.