the speakers that are on top of the dash under grills. How do you remove the grills to install aftermarket speakers?

They pry up.

Yes they need to be a very shallow and you need to cut a bit of the dash, I have got 4" Sony explodes in my dash. They are a real prick to get out and replace :)

when i put my splits in, i just cut two of the mounting points off the speakers, opposite each other. does not affect strength and they fit nicely.