I can confirm the Canadian Nissan Hitch, Part # 99998-6475-29 is in fact a Hidden Hitch.. its even stamped as such. My first dealer hitch cost me $169.40 + tax in 2000, my second (got rearended) $188.22 + tax. I also installed the same exact hitch on a 2002 SC. Install is very easy.
This price was for the hitch only since I already had a receiver & ball for them. (which would be cheaper at Cdn Tire)
If you don't know already, there is an Xterra Club in Ontario with loads of info. Hit the link in my sig,