-You WILL have to splice the old harness into the new harness. It is not plug and play
-The bolts can be found at your local big box hardware store(Home Depot, Lowes, Ace, TrueValue, etc......)
-The cubby hole, 12V, and 120V all come out as one piece and will not be reused. The top trim ring you order will have those in it.
And as far as installation I would re-read this thread as all those questions(including the ones I answered above) are in this thread.