Introduction
Many Acer 15" Chromebooks use the same keyboard, including the C910, CB3-431, CB3-531, CB5-571 and possibly others, although the palm rest assembly is the same only on the CB3-531.
There are new keyboard-only replacement parts for sale, but using them requires melting off or otherwise removing the head of approximately 58 plastic retaining pins, then figuring out how to re-secure them. That kind of replacement is beyond the scope of this guide, so we'll only be dealing with a replacement that comes with a keyboard + palm rest as a single unit as pictured above.
Tools
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            Using the Phillips #1 screwdriver, remove eighteen 7 mm screws from the back panel of the device. 
 
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            Use a plastic opening tool around the edges of the laptop and remove the back panel from the device. 
 
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            Push on the sides of the connector with a plastic spudger to separate the cable from the motherboard. 
 
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            Firmly pull the end of the black wire attached to the Wi-Fi card upwards and remove it from the device. 
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            Repeat with the white wire. 
 
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            Pull the end of the display cable attached to the motherboard straight up to remove. 
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            Rotate the cable out away from the motherboard. 
 
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            Insert a screwdriver or spudger under the hinge to get it started then rotate it open by hand as far as possible. 
 
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            Insert a screwdriver or spudger under the hinge to get it started then rotate it open by hand as far as possible. 
 
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            Lift the palm rest assembly from the front then slide it away from the hinges slightly to remove the assembly from the display. 
 
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            Using the Phillips #1 screwdriver, remove the three 3.2 mm screws holding the touchpad to the laptop. 
 
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            Carefully lift up on the keyboard ribbon cable and the insulating sheet immediately below it so the touchpad can clear them. 
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            Lift the touchpad slightly from the top. 
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            Pull the touchpad toward the motherboard as you continue to lift it, sliding it out from under the retaining fingers at the bottom. 
 
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            Remove the touchpad. 
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            Make sure the touchpad goes underneath the two retaining fingers when reinstalling it. 
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            The touchpad is correctly aligned when the guide pins next to the left and right screws are inserted in the holes. 
 
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            Thread the speaker under the black ribbon towards the left to allow removal of the left speaker. 
 
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            Peel the yellow tape off the black keyboard ribbon cable on the motherboard. 
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            Use a spudger to slide the black tabs on either side of the connector forward slightly. 
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            Pull the black ribbon straight towards you to remove it from the motherboard. 
 
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            Flip up the tabs over the two white ribbons on the left using your finger. 
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            Pull the ribbons out of the motherboard by the blue tabs. 
 
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            Using the Phillips #1 screwdriver, remove four 6 mm screws. 
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            Using the same Phillips #1 screwdriver, remove five 3 mm screws securing the metal plate to the motherboard. 
 
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            Grasp the ribbon cable by the blue plastic reinforcement and pull the cable straight out to the right. 
 
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            Remove the single retaining screw securing the LED board. 
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            Remove the board. 
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            When reassembling, ensure the board is seated on the guide pin before reinstalling the retaining screw. 
 
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            The cable between the I/O board and the motherboard is lightly adhered to the plastic insulator on the keyboard. Pull up from the right to free the cable from the adhesive. 
 
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            The LED cable runs from the LED board to the I/O daughter card. It is lightly adhered to the keyboard. Remove it by gently pulling it away from the keyboard. 
 
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To reassemble your device, follow these instructions in reverse order.