No need to go under the dash. Just take the wiper arm off its post and relocate it somewhat away from the side it goes down off the glass. Take a little piece of wood or a piece of thick cloth to put under a claw hammer to carefully detach the arm from the post. Pull as if pulling on the edge of a nail head, except with more caution, because the bottom of the arm fits over the post by about 1/2 inch. You have to kind of hold it straight when you put it back on, due to the tension in the arm, which is designed to keep wiper pressure on the glass.
I've used silicone around the windshield rubber for years. If it starts to leak again I just renew the silicone. I mask off the paint and the chrome, and then the glass and the chrome to keep it neat. I use a caulking gun size of black silicone and smooth it out with a razor or butter knife. When I have it nice and smooth I pull the tape off.