Hi, so sorry you are going through this.
I had a long career in intensive care and have nursed so many patients in a similar position. As well as caring for your Dad, the nurses are there to support you as his daughter.
You will be given as much time as you need and may be offered some keepsakes like handprints/hair locks or photos of his hand holding yours, depending on what resources your hospital has available. He's still your Dad regardless of the tubes, machines and flashing lights.
I have regularly been able to facilitate moving a loved one over in the bed so that family can get on for a cuddle - the more experienced ICU nurses know exactly how to do this safely.
The actual process of withdrawing life sustaining treatment depends on several things, the main one being how much awareness he has and if he is able to breathe spontaneously without the ventilator. If he is able to take spontaneous breaths, it may be decided to "extubate", where the breathing tube is removed and nature allowed to take its course. This can be minutes to hours to days depending on his ability to breathe. If he has so little brain function proven by scan or special brain stem testing that he cannot take a breath, it isn't always necessary to extubate, the ventilator can simply be switched off along with any remaining inotropic drugs supporting his cardiovascular system. Whichever happens, the bedside nurse will liaise with the medics to ensure he is pain free and as comfortable as possible and often as much medical equipment as is safe to move is moved away to make the area less clinical. Pre pandemic, I often asked family members to bring in special blankets or even football shirts to personalise the space.
I have supported a massively diverse range of families through this process from large, extended families, warring families and single family members at the bedside as well as patients who had no family, in which case I have sat quietly and held the hand of the patient. The monitors can be turned off so you are not distracted by numbers and machines - you don't need to be a medical professional to know the precise moment things change as the person passes away.
No one can tell you exactly what will happen as no two people are the same. Let the nurses guide you but don't be scared to speak up if you're uncomfortable or worried. Most ICU nurses are amazing at taking the time to sit down and just be there if required.
You will be given so much information, but don't worry if you need to ask a million questions - nobody expects you to retain it all. The most important information will be given to you in written form, for example - what to do next, who to contact etc. All of those things don't need to be done immediately though. Take the time you need. There are bereavement specialist nurses who you can lean on as little or as much as you want, and access to people who know exactly what next steps are the most important.
Take care of yourself and be proud that you are there for your Dad. I remember my Dad saying to me when he was days away from dying on end of life care "you don't need to stay here, you've got a busy life" and me telling him "if the roles were reversed, is there anything in the world that would stop you from being with me?" - he knew the answer and didn't try to banish me again.
Sending love to you and your Dad x