mapping navigation bar

Hello,

I have a wp Blog designed as a static website where one navigation menue point refers to the actual blog. I decided to move the actual blog (not the whole website) to a more generic domain. Now is it possible just to map this one point in the navigation bar to that new domain or is it in fact better to use a plugin like “page links to”?

Secondly, is there a danger that google sees the remaining parts of the website (header etc) under the new domain as dublicate content?

thank you!

http://ww.wp.xz.cn/extend/plugins/wordpress-mu-domain-mapping/