Hyundai Repair: code 720 input speed sensor fault, mitsubishi dealer, vehicle fluids

Question
I have a 2001 sonata with a 2.5 v-6 automatic trans that will kick a 720 code about once a week. I have a new sensor in hand and I would like to know where it is located and will I have any problem changing it out. I have had similar type sensors in other vehicles that seize in and are almost impossible to remove. Any insight will be appreciated .Also I want to change the fluid and see what I believe to be a main drain on the very bottom,is this right? I will be buying the fluid from the dealer unless you tell me there is another available fluid that can work. Thanks for any help Thomas.

Answer
The output speed sensor is bolted into the top of the transmission, almost exactly under the front of the master cylinder.  As it's plastic, you should expect it'll come out easily with just a little twisting.  

The 24mm plug on the bottom of the transmission is indeed the drain plug.  Use only SPIII fluid.  You can check with your local parts store, but I'll caution against "multi-vehicle" fluids which claim to meet numerous specifications.  You want fluid that is specifically labeled SPIII and nothing else.  If you cannot source this at your local parts store, you should be able to purchase it at any Hyundai, Kia, or Mitsubishi dealer.  Expect to use 5 to 6 quarts on a drain and refill.