I currently have a store using Magento 1.6.1 and want to update to 1.9. Can anyone give me some advice on whether I am likely to get any conflicts if I link the existing database to a fresh installation (same URL). I have read around the subject but can find no easy answer on this.
there will be some issues, but, you will be able to fix them easily.
obviously you will have to change your theme and upgrade extensions.