You sound very unsure of yourself and i can completely understand as i was in exactly the same position last January when i got a call out of the blue asking if i fancied skippering a brand new 74' motor yacht. Yes please i said. To be honest i had to blag my way through. I have absolutely no worries about my boat handling skills but my previous boats (as a driver) were a 46' sailboat and a 57' sailing cat that did day trips for tourists
I'd worked on 1 mega yacht before but apart from that i was completely green. The owner understood this and fairplay to him, he gave me a chance. I was worried as hell when i picked the boat up from the yard.... luckily 1 of their skippers had arranged to take it to Southampton docks to be shipped to the med so i got some time as an observer before i had to meet and greet in gibraltar.
I was still mega worried but took it bit by bit and eventually learnt all the boat systems and things such as the questions you are asking. It's natural to feel very unsure but i can assure you that if you get the job and don't crash her in the 1st week, you will look back on this thread and smile. It's easy peasy weasy once you get into the swing of things. Other skippers are usually more than happy to help if you have any questions too.