Yeah, a write up is pretty difficult for this, as there is really a lot involved, not just in terms of wiring, but as you would have found out by now, physically removing the old, and fitting the new head unit can be a little tricky the first time you do things.
Also, very few people have performed this upgrade, and very few of those people that have have shared information. (With the exception of doubledip, whom has been a big help to me).
My suggestion is to print out the above wiring guides, and work out what wires you need, and what ones you don't.
Think of the wiring as the same as wiring a top end head unit, that has connections for reverse camera, power antenna, handbrake, amp enable, reverse gear, etc and that you are replacing one brand with a completely different brand.
Even thought the plugs will physically fit each other, the pins are completely different.
If you wanted to make things easy for yourself, find the power and can bus wires, connect those up properly, and cut the rest.
That will get the head unit up and running, and then you can proceed to wire up the extra bits at your own lesure.
Finally, I noticed that you have a sat nav model.
You will probably want to look at fitting a series ii cluster at some point in time, as the sat nav prompts get corrupted on series I clusters to the point that it will p!$$ you off no end.
(Think speed camera, school zone and cluster nav alerts, they change the cluster display constantly, requiring you to press the Trip button to return to whatever mode you were using before.
These IQ upgrades can get pretty expensive pretty quickly
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