Being the intrinsic mechanical contraptions they are, cars, more often than not, require repairs to be carried out by a professional due to the hazardous nature of some of them.
A car repair, or rather an upgrade, seemingly as simple as changing your radio to a DVD player, involves proper knowledge of electrical wiring. One wrong move can seriously damage your car, leading to a short circuit or, even worse, an electrical fire.
Similarly, replacing the shock absorbers or brakes of your car is a popular do-it-yourself repair, however, getting it wrong by the slightest can make your car a dangerous vehicle to drive.
So unless you have been doing this for a very long time and have become proficient at it, it is a repair you better leave to the professionals.