The screw is kinda hidden on the side where the door meets the dash and the speaker grill just kinda pops out toward you. Sometimes you have to work it a little from be'n stuck in place for 25 yrs or more, just don't force it.
Wow! It's two screws that hold the cover on. You're probably gonna have to use a short Phillips head screw driver (The kind that looks like a cross). A long screw driver would probably just booger up your screws.