I did the fix as expertly described by PaulW. Took about 30 minutes, as I hadn't removed the panels before. The orange plug was really gunked up. I actually pulled the orange J drain out and flushed it in my sink. Easy to pop back into place.
Now, the question remains, why is my A/C ducting filling up with rainwater. I read a previous post (see link), that describes two problems:
1. the drain around the air intake gets gunked up; easy fix is to blow compressed air around the intake. I imagine I am to blaim as I've been parking outside, and all the leaves must be clogging stuff up.
2. The seal that protects the air intake from the outside environment (i.e., water) breaks down with age. This I would like to address somehow.
If anyone has the repair manual or a quick solution to this problem (e.g., some type of caulking), please let me know. Ever grateful to the forum, and contemplating getting out of this tumultuous love affair with this automobile.