1. Just before starting a surgery, in the top, right corner of the screen, there will be an Advanced Pre-Op icon. Pressing it will activate it for the upcoming surgery. You'll know if your Advanced Pre-Op is activated when the icon is lit up (instead of being grayed out) and when the heart amount has increased.
2. You can find this heart counter on the top of the screen next to the surgery time.
3. This is the operation time and the amount of time you have to complete the operation.