Just finished replacing the main belt in my '89 2.6. Thanks to everyone whose input to this site made the job look possible. I finally have something to contribute.
Here's my procedure:
Remove the three fan shroud clips; one on top next to hood release, one on top drivers side, and one on passenger side down about 6".
Manuever the fan shroud to get access to the three nuts that hold the fan blade. Breaking these nuts free was a real pain but once loose, I was able to use my fingers to spin them off. Remove the fan blade.
The shroud was too big to remove between the radiator and fan clutch. I noticed a plastic clip at the top of the shroud that, when squeezed together, allowed the shroud to break down into two smaller pieces that COULD be removed between the radiator and clutch. The two shroud halves must be rotated in opposite directions after releasing the clip to break down into two pieces. Remove both section of the shroud assembly.
To loosen the 19mm nut on the belt tensioner, I used a standard 3/4" (I didn't have the 19mm) socket on a very short extension. I loosened it about 3 turns. Then I loosened up the belt tensioning nut with a 13mm socket. Note - When I was trying to find this nut originally, I couldn't get a good feel for where it was based on the information I found. The good news is that it is a long hollow nut located right above the belt tensioner assembly. It's directed almost straight up. In other words, if you could get your head down into that area, it would probably poke you in the eye! There is a wedge shape cast into the top of the belt tensioner housing in my car. The thickest part of the wedge is on the left and it decreases to the right. The plastic 'pointer' on my car was aiming at the middle of this wedge. I understand that the pointer should move toward the right when loosening tension, but mine didn't move very much. If you pull up on the belt while loosening the tension you can feel the tension ease up (and see the pointer move). Before removing the belt, note the routing of the belt.
My owner's manual included the belt routing diagram:
Remove the old belt.
Install the new belt. Back to the tensioner! Manually push the pointer all the way to the right. It may click a few times. Now tighten the 13mm tensioning nut. The pointer should start to work it's way toward the thick part of the wedge. When the pointer gets there, you're done. Now tighten the 19mm nut to lock everything in place. You've finished the belt installation.
Put the two pieces of the shroud assembly back in place. Take a deep breath, be patient, and try to get all four corners aligned and rotated back into place. Use the plastic clip to secure your handy work.
Do not secure the shroud until the fan blade is installed. It is much easier to get your hands in there if the shroud can be moved around. Install the fan blade. Install the shroud into the two slots near the bottom of the radiator. Use the three clips to secure the shroud near the top of the radiator.
If I forgot something important, feel free to comment.