Having a body kit installed on a car is a pretty huge commitment. A body kit consists of front and rear bumpers, spoilers, side guards, and paint. Factory pieces will be removed and aftermarket parts will take their place. In many instances, the car will need modification to accommodate the kit.
With anything that will drastically change the car's appearance, it is important to be patient and measure everything twice, otherwise, the end product could turn out looking mismatched and cheap. Some kits are simple enough to install yourself, but for most, it is best to have a professional do it.