iFixit

Disconnect the iSight, inverter, and left fan cables from the left side of the logic board.

Take care not to dislodge the EMI gasket on the silver iSight connector.

If you have a MacBook Pro 17" Model A1229, the iSight, inverter, and left fan cables have different composures and locations.

For model A1261, the fan cable is located in the same location as the model A1229, 5 o'clock to the fan. The iSight and inverter can remain connected. Lift the tape from the top of the fan and make sure to check the connections afterward.

Peel up the iSight and inverter cables which are attached with a mild adhesive above the left fan.

The iSight and inverter cable can optionally remain connected.

Remove the two silver T6 Torx screws securing the left fan to the lower case.

Lift the left fan and its metal bracket out of the computer.

The tape that covers the top of the fan can be reused if the fan is removed carefully. Pivot the fan towards the screen and very slowly pull bottom of the fan away from the tape from left to right. It should peel off without stretching if done slowly. Then slide the new fan under the tape and press the tape back on the top of the fan.