empty master cylinder

been noticing the brakes getting softer so pulled the cap on the mstr cylinder and one side is empty. i've also noticed small amt of fluid after she sits all nite which i wonder is brake fluid. i can pull the front tires and check pads and rotars but i'm concerned about the calipers. could this be a job for a novice or should i turn it over to a shop? whats a totalmrebuild cost? thanks