I have an 06 Lt and i have installed an after market double din in dash player and removed the door speakers and switched those out as well.
Its honestly the easiest car i have worked on for the head unit. The trim where your radio is just pops off. I have the wood grain on mine so its pretty easy to determine the outline. Make sure you disconnect the passenger airbag sensor that plugs into the Radio trim. After you remove that there are 6 screws that have to be removed, First remove the bottom two screws (the ones that hold the the a/c control) so this way the a/c controls can drop down some and you can pull out the radio. Next remove the other 4 screws holding the radio and pull that out and disconnect the antenna and the wiring harness from the back of the head unit and you are done wit that.