The 2 main things you will need when installing your new stereo is a wiring adapter and a dash kit.
The wiring adapter is a piece which has a plug on one end and wiring sticking out of the other end. The plug connects to the factory wiring, and the wires are connected to the matching color wiring on the new stereo. This allows for connecting a new stereo without having to cut the factory wires.
Stock stereos have varying sizes, and if you just place an aftermarket stereo in the hole left by a stock stereo then there will be gaps around the stereo. The dash kit is a plastic piece which fits into the hole left by the stock stereo and fills in the gaps between the aftermarket stereo and the dash.