Quote Originally Posted by LadyoftheCave View Post
will I then not override my old product-lines?
Yes with the data that was there at the time of export, which other than a change in quantity that may have occurred between export and import should result in no change. This also is why it is suggested to make a database backup before importing, especially when first trying out something. Even more of a reason to test new software on a development location that doesn't affect your business...