Its a very personal thing as to how much you can get off the price and how much you can get chucked in, depends on who you speak to (ie sales man or sales manager), and how hard you want to push them. As a marker, I'd aim for 10% off a cars list price and see how far you can go, When you've pushed them to the limit on price, then talk about the freebies. How hard you push depends on if you want to feck them off or not. If you plan to have them do the servicing and any warrenty work, its not worth annoying the hell out of them to get a few freebies for them to then take a dislike to you!
You'd have to speak to Nissan dealership about the satnav, havent seen that deal until now.
For the kick plates, they are alu and illuminated like this: