its a direct swap...
inside the door panel, you will see a cover right behind the back of the mirror. If you pull it, it will pop off. behind it is the wiring harness and the 3 nuts that hold the mirror to the door. unplug the harness, and remove the 3 nuts, and do the reverse to put the new ones on
you can buy the parts from
Nissan Parts Online - Discount Genuine Nissan Parts & Accessories Online
Part# 96301JB14E, 96301JA04C, 96302JB14E, 96302JA04C
only problem is covers come unpainted so you would have to get them painted unless you know someone whos selling them painted, do let me know since i was thinking of doing this in the next few weeks