I have an 04 Mada LE and I dont have the nav system installed. Can the stock navigation system be bought from Nissan and if so does anyone know how much it would cost?

You can, but honestly it would be cheaper to go aftermarket, and you'd get better features. You can buy the factory navigation bezel and have an aftermarket touch screen installed cheaper than going with the factory system.

Do a search for "navigation" and you'll get tons of info.

I second that.