Hi I am doing the oil galley gaskets on my HR and am about to take my timing chain off. Few questions.

Why are the timing marks on the chain relevant? If cams and crank are set to tdc can I remove old chain without lining marks up or should I line them up?
My understanding is it takes 41 rotations for them to line up. Is this correct ?

Also any tips on how to get to the screw for the oil galley cover that is directly behind the passenger side camshaft sprocket ? Seems removing the passenger cam chain/cams would be the easiest method ?

Thanks guys