1. Unfortunately, you cannot replace the wiper shaft seals without pulling the dash! It's a real pain....
2. I found a leak on my passenger side footwell (basically where the toes on your right foot would be while seated in the passenger seat) where the fender meets the firewall. There are drains on each side that get clogged. It's extremely difficult to see, but from underneath you can see light if the drains are clear. This actually rusted a hole through my upper floorboard! I was able to fix it by welding in a patch. It was very hard to diagnose, but I noticed it would get wet even when it wasn't raining but the roads were still wet enough to kick water up in there.
I hope that makes sense! It took me months to find, but I was quite relieved when I finally did.
Good luck, Tristan