The dash tweeter grille assembly simply pries up and out. Take a cloth covered, flathead screwdriver to the edge facing you, and gently pry. The tweeter is attached to the bottom of the grille on a metal bracket. People who reuse this location tend to fit their aftermarket tweeter on the bracket with some double-sided tape to secure it.

The comment about the dash location not being optimal is absolutely correct; the windshield creates undesireable reflections. I have seen a number of installs that put the tweeter into the upper-forward door panel, and one that modified the sail panels to hold the tweeter (I'm still curious if someone could use heat to deform the sail panels to fit a tweeter; I've seen the technique successfully used with A-pillars).

Personally, I decided that a hole in my door panel wasn't worth the acoustic benefits.