How to convert from NAV to Norton Internet Security using CD

I have Windows XP Pro running Norton Antivirus that expires in 3 weeks.  I purchased at Staples the Norton Internet Security CD but don't know what steps are needed to convert from the NAV to NIS.  Do I need to delete the old program first using the Norton Removal Tool?   Can I just load the NIS CD without doing any clean up first? Thanks for any help.

Richard