VXOC Astra-J/GTC

Hi there. I know there's a few amazing threads and how-tos showing how to upgrade to a touchscreen HU, but I had some questions:

My 2013 Astra J has the Navi 600 with the colour screen. I've looked at the options available for example in the Android Auto section of caraudiodirect (http://www.caraudiodirect.co.uk/head-units/android-auto). Can one of these just be swapped with the current screen using a new surround and the relevant loom, or does it have to go where all the controls are and I need to swap out the whole fascia?
And if the latter is the case, will I have two screens and is the original one just redundant?
Also, do the controls in the steering wheel still work with these HUs?

Thanks in advance for your help!

If you go down the double DIN route the wiring will need to be changed to a CD400, you would also end up with 2 screens.

Which ever route you take even going for an android OEM looking unit you would still need to make the wiring into a CD400.

Thanks Rusty.

If I'm needing to change the wiring is that just a loom or adaptor, or are we talking actual clipping and potential soldering kind of wiring?
And is it possible to get an Android Auto supported HU that could just replace the top screen? The only ones I can find are just Android HUs. They don't mention that they do Android Auto.
(As you can probably tell, having Android Auto is quite important to me  )

You don't need to cut and solder wires much easier to just remove from connector/s and put new wires in.

I'm sure on the units TBH.