No. A well tuned sprinkler system will actually save you money over watering by hand. Sprinkler systems are designed to deliver only the amount of water that the lawn or planting bed needs while hand watering offers little control over the exact amount of water delivered.
Yes. In fact, an automatic sprinkler system will water better than watering by hand because it can be set up to give each individual plant exactly the amount of water it needs at the best time for it to maximize its effectiveness. It is also on a set schedule, so the plants get their water delivered in a timely manner. Hand watering often happens only when a property owner has time to do it.
Sprinkler systems can be equipped with rain sensors that will automatically shut off a sprinkler head when enough water has been delivered to a specific area of the lawn. These sensors can be installed on existing pop up heads and drip irrigation lines in any area of the system.
While there is nothing stopping you from installing a sprinkler system on your own, it is in your best interest to at least consult a professional before doing so. Sprinkler systems are extremely technical and require a great deal of care when adjusting. By installing one yourself, you probably aren't going to achieve the efficiency that you could with a professional installation.
Automatic sprinkler systems, once optimized, will run on their own without any intervention from the property owner. Some systems can even be controlled by a PC or Smartphone application.