The dealer usually contacts you cause they want the business but it’s your responsibility to ensure it is done on time, just call them up to get it booked in. You can go to any garage that services your make of car, you are not tied to the one it came from.
You only get a curtesy car if you request one, if they have one available and you may have to pay for the insurance… book early to give yourself the best chance of getting one. Otherwise many garages will collect and return the car from your house/work etc.