I had the same radio in my car.
What you end up needing is:
1) Double DIN radio, and a fascia adapter, you also need a bread-knife / dremmel / whatever to make some minor mods to the plastic behind the radio, and the ‘keys’ to pull it out, and maybe the metal ‘box’ the radio sits in if it doesn’t come with one.
2) adapter from your new radio to ISO (or whatever the wiring harness standard is called)
3) Adapter from that to your car (who the **** knows why they don’t just make cars/radios the same)
4) Adapter for the stalk bit (this is a little black box with wires coming out as it has to do some basic computing)
5) You might need an aerial adapter too, but I didn’t and have a ford and the older version of that Alpine radio.
To be honest, if you don’t know what your doing already, just take it to halfords and get them to do it. Unless you can get a brilliant deal on a stereo elsewhere it’s not worth the hassle of trying to figure it out. Took me half a day and I probably saved £30, not worth it.