This is done on a right hand drive UK Focus. The process should be more or less the same, just take into account that some things may be flipped to the other side.

 

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How to Remove Head Unit Radio for Ford Focus 2008

Ford Focus SVT Aftermarket Radio Wiring Connection

So below are the pieces that I’ll show how to remove, labelled in order.
I started by removing the whole radio unit. This is really easy and takes about 20 seconds. Above the temperature control is a small piece that is easily removed with pliers. Behind this piece are 2 screws. Unscrew them and the whole radio unit can be pulled up and away from the car. Disconnect the harness behind the unit.

1.) Vent Trim Panels

These are attached to the radio unit, and can be popped off by simply pulling/prying from the bottom (label with an arrow above) moving upwards. If you come across a stubborn clip, get a flathead screw driver, get it between the radio unit and trim piece and push the clip inwards towards the vent opening.

2.) A/C Control Panel
There are 3 screws (indicated below). To access the side screw you will need to slightly pry the adjacent trim panel away. Once undone the panel can be wiggled out, disconnect the harnesses behind the panel and pull out of the console.

Behind the A/C control panel there are 4 screws (indicated) that will detach the knobs. The 2 sets of buttons below the knobs (also indicated) are removed by squeezing tabs on the backside.

3.) Shifter panel

To remove visit this how to, courtesy of Twenty

http://www.focusfanatics.com/forum/showthread.php?t=273852

So this is what your radio area would look like with everything removed. Circles indicate the radio screws, squares the A/C control panel screws

4.) Parking break piece
For this I just pryed the with a flathead on the side, near the bottom end. It popped out quite easily. I recommend not using too much force here, as it is not needed.

5.) Door trim
You must start prying at the front end (indicated by an arrow). Just because of how it sits in the door. The rear end is inserted into the door at an angle which prevents it from being pryed.

Enjoy! Feel free to ask questions.