You will need a scan tool called SST - 09843-18040 to read the transmission temp. Dont Drain until you have one, it is about 3$. IT is available with the local dealer. It is very easy once you have all the stuff. Ensure to purchase the following
1. Transmission Drain Plugand Over Flow Gasket - P/N - 35179-30010, and you need two. You also need to replace the Fill Plug O-ring. Ensure to bring the original to any autopart store to match. You need to buy 4 quarts of Toyota WS fluid. I use a scan tool which i have recently for my laptop from
http://www.autoenginuity.com/, after a recomendation with advanced features for toyota or lexus.