For vehicles that have stock steering wheel controls (or I believe you can also buy aftermarket ones), just plugging in a new deck with harness will not retain functionality of them. For those that want to retain them, adapters are needed.
That's the mic for the auto tuning. Read through the manual for a complete description of it as I haven't played with mine yet to give you a full explanation. I very much dislike the lack of a paper manual now, my CD manual has been in my computer for about a month now and I have read to bother looking at it.