How do you remove the rear 6x9 speakers to install new ones?

It depends on how the speakers are installed. Either the screws or bolts should be accessbile from the underside of the 6x9 speakers through the trunk of the vehicle. If you don't see screw heads under the speakers, then remove the net covering the speakers on top. This should expose the screw heads. To remove them are actually quite difficult. First remove the back seat cushion by pulling straight up. Exposed in the corners where the seat meets the door are 2 screws, one on each side, remove those and slide the whole cushion upwards. Then remove the couple black screw holding the back panel on. Then remove the center brake light cover and screws, then slide the whole back panel out. Then the speakers are each held in by 3 bolts. Remove them and replace with whatever you want.