Take the negative battery wire off the car before you can take out the radio in a Chevrolet TrailBlazer or Chevrolet TrailBlazer EXT. For Chevrolet variants, start with the lower center insulator panel of the instrument panel, then unfasten the accessory trim plate that sits on top of the panel. Take off the mounting screws, carefully lift the radio out of the instrument panel, disconnect the connectors, and pull it out completely from your vehicle. Just do everything in reverse when putting it back in. Take off the trim panel to access a door speaker, while for front dash-top speakers, begin by taking off the panel above the instrument panel. First, detach any screws keeping the speaker in place. Pull the speaker directly out and disconnect the electrical wire. Take the speaker out of the car or truck.