Based on other references (another model year), I took a chance and was right. The retainer bolt for the tensioner pulley is indeed left-hand threaded - this means to loosen you crank it clockwise, and to tighten you crank counter-clockwise. The one in my 03 TL-S is 14mm. Of course removing the serpentine belt is the first order of business. You can rent a loaner tool from the parts store to relieve tension on the arm in order to remove the belt.
Other important information: there is not enough room to clear the bolt once it is out of the hole in the tensioner arm. In fact, once I got the bolt out of the hole, I just poked the pulley until it, the dust plate, and the bolt all dropped together. I had taken off the wheel at this point so I could attack (poke) from below.
To reinstall, it's best to do the same type thing - take the pulley, plate, and bolt together (assembled), and slide it all between the tensioner arm assembly and frame. Then try to angle the tip of the bolt into the hole of the tensioner arm and get it started. I'm not gonna lie to ya...this is not easy. Or I should say, it wasn't easy until I figured out a good strategy. The best strategy is to get a person to help you guide it from above while you support the pulley from below. Since I couldn't find anyone when I needed them, I took the pulley, plate, and bolt (assembled together), carefully slid it all in first from above, worked it below the tensioner arm, then gingerly brought it back up until the tip of the bolt was resting in the hole of the tensioner arm. At this point, with the tip of the bolt sitting in the tensioner arm hole, and the pulley, plate, and bolt head resting against the car frame, I got back underneath the car and reached up to CAREFULLY grasped the bolt head between my thumb and forefinger, and started the bolt into the hole; if you get too agressive with this, the whole thing will fall and you will have to start the positioning process all over again. PLEASE NOTE that since the pulley retainer bolt is left-hand threaded, it has to be twisted COUNTER CLOCKWISE to start and tighten the bolt. Once the bolt is started, you are home free. It's easiest to hand tighten (remember, counter clockwise) as far as you can, then finish it off with a wrench.
Now reinstall the serpentine belt. I had trouble with the belt coming off the crank pulley while trying to maneuver the belt around the other pulleys. To help hold the belt still, I got a pry bar and stuck it through an opening in the top of the engine bay, and let one end of the bar rest on the belt on top of the crank pulley. Now with the pry bar holding the belt in place on the crank pulley, I could use the loaner tool to compress the tensioner pulley while working the belt around the alternator and a/c compressor pulleys, and finally under the tensioner pulley. Done!
The bearing on the old pulley was definitely bad; once removed, I could hear and feel the clicking when I stuck my finger in the bearing hole and turned the pulley by hand. This was causing an annoying sound from the engine bay, and I had located the culprit by using a crude stethoscope - a rubber hose. In addition the sound of the bad bearing, the vibration was also causing the pulley's dust plate to 'sing' at certain RPMs. But with the new pulley in place, no more noise