Unfortunately, no. The hardware that comes with a new HU is a stupid "cage" that kinda wedges itself into the dash openning of most late model cars. It won't fit your Caddy. You be gonna hafta make it fit yourself.
And you gotta be real careful about making the cutout, because the faceplate bezels on todays HU's are only about 1/8" bigger than the deck. They won't cover your mistakes if you make the hole too big.
You get a wiring harness, but you'll also want to buy an adapter harness that plugs into the car's existing connectors. That way you don't have to cut the GM plugs off your car's wires. At least those are available for your year.
My Avitar is a reduced pic of my dashboard with the Pioneer installed. If done with care, it can look perfect (like mine //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif )Professional installers do this all the time. They're in the yellow pages.
I sent you a link to my web page that shows my install.