I'll agree that radio should be provided by a head unit, it's just easier that way. It seems that motorized screens aren't recommended by people here, because they aren't considered reliable. Perhaps it is possible to put the head unit somewhere else to make room for the screen? In my setup I'll have the original HU behind my netbook carPC.
Maybe you could move the HU further down the centre console, into the storage area?
That would probably require some work, especially to make it look like it belongs there.
I can't help much with the mac as I know nothing about them. Anyway good luck with the install.