Aftermarket head unit

I know this has been covered before, but I did not see a recent thread.

So if I buy a later STS, like a 2010 Cadillac STS premium with Navigation, can that head unit be successfully replaced?

I read in some threads that it would require the current head unit to the trunk. I would have all this professionally installed.

So has anyone done that, how did it come out? Can you still use Remote Start?

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Also keyless entry, steering wheel controls, etc