nice one mate
WELCOME TO THE FORUM
my 2cents - get nissan to do some of your first extras..
my example - if you plan to take delivery of your Nav and drive it straight around the corner to put on new wheels and tyres, let Nissan do it - even if you have to have some organisational part in that. the reason for the suggestion is nissan then won't be selling you their wheels and tyres and therefore you won't be paying for them. your upgraded wheel/tyre package will still cost ya thousands but at least nissan will write ya a cheque for the unused ones you won't need.
only a thought and an example of what ya could do - good luck with it