what will come out is the whole setup: the actual head unit, the harness will get unplugged, and the metal cage (sort of like a metal sleeve with a bunch of holes and slots in it). Once you get a hold of the DIN tools to pull the stock HU the rest should be easy (though both my old Ford Probe and my Typhoon had DIN holes in the stock head, and I was able to get it out without the tool...you might want to check and see if there is a plastic border around the HU that just pulls off and reveals either philips or flathead screws attaching the cage to the dash)
When you put the new one in you have to splice the harness onto the new HU, then connect it to the other part...slide the HU into the new cage (should definitely be in with the HU in the box), and use a screwdriver to push some of the slots up into gaps in the head unit (holds the HU in place). Then slide the cage into the hole, screw down, and you should be good to go.
Anyone who finds a discrepancy in here is more than welcome topoint it out...this was the exact process I used to get the Pioneer HU into my truck, and I have not yet had to install a HU into a Tour.
