iFixit

The connectors at the ends of the cables are attached very firmly to the sockets on the logic board. Pulling directly on the cable will either separate the cable from its connector or the socket from the logic board.

Lift the upper case enough to disconnect the blue and white power cable from the logic board. Using your fingernails or a dental pick, carefully pry the connector from its socket. Make sure you're pulling only on the connector and not on the socket.

Lift the upper case off completely and disconnect the multicolored speaker cable from the logic board. As before, make sure you're pulling only on the connector and not on the socket.

Tip: the multi-coloured cable may be easier and less daunting to disconnect after removing the top heat shield. Prop the top case upright while removing the shield - the connector is then much more accessible.