1stlink,
Florida heat tells me you should flush out that old fluid and change the tranny filter, but don`t go to Lexus to pay through the nose. A good independent mechanic can do the job for you for dollars less.
I had the timing belt and waterpump done on my 04ES at about 90,000. I also had all the fluids (except oil) changed. Transmission, power steering, brake fluid and coolant. Had it done at a Toyota dealership for about $800