To remove your head unit:
If you are removing your standard radio you will need specific keys to suite that model. You can obtain these easily from ebay. When you insert the keys they will push the prongs at the side of the head unit, and unlock it. You will then be able to slide it out. This can be pretty tricky on some models, so be careful not to break any thing. Once you’ve slid it out you can then unplug the wiring, and remove the cage.
Its important to get the radio code, as once you have disconnected it, you will need the code to turn it back on.
To install your head unit:
Most Head units will come with a cage, and an adapter plug. First you need get the plug that converts your car to ISO, unless it’s a modern car, which would already be ISO.
Push in the cage, and make sure you push the metal cutouts down, so that the cage cannot be removed. This stops theft, and makes it stay still. You will need to screw the rubber stopper onto the back of the head unit. This also keeps it stable and aligned.
Next attach all your wiring (you may need a DIN to ISO converter for your Arial lead), and push the radio in. It will click into place. Now all you need to do is clip on the facia plate, and your done.