Can I upgrade a new copy of NAV 2009 to NAV 2011 after activation

I recently purchased what I thought was a new NAV 2011 product for very good price on the Internet, but now I am having doubts about it's validity. It was advertised as NAV 2011 but when it arrived it was a NAV 2009 disc with instructions on how to upgrade it to NAV 2011 using the  uk.norton.com/downloads  site.

Have I been conned ?.  It is a Symantec System Builder Edition with a Product  Key.  Will the procedure work or will it be rejected ?

I currently have NAV 2010 on my PC with a license that expires at the end of March 2011. It has been upgrade free by Norton to NAV 2011 until expiry date.

I would appreciate an answer to my dilemma, so that if necessary I can return the product for a refund.