If I already have a Bose nav system in my altima coupe do I need to replace the dash kit to get another nav head unit. Would the old fit the new?

Yeah you actually need a new dash kit because the Bose nav is a little too wide. Now if you have the automatic climate controls with the digital screen than there isn't one available for you... Ill need to check on that to be sure.. But if you have the manual climate controls than Nissan makes a dash kit for aftermarket navs that fits perfectly and looks stock.