The bose amp is located under some foam in the boot which is a bit fo a mare to get to. There is also a 2nd sub amp which is located in the sub box. Do you have a sub behind the driver? If not have a look behind the panel and you should seee on the back of the metal sub surround a black box..if you have one that is.
You may find the car never had BOSE and then you can just use the looms that are there.
As for bluetooth - the Nissan unit does not really work with any aftermarket head units, only the factory ones