Hi David,
Due to the gap between versions, you may run into data conflicts when re-importing your existing data to a newer release as new fields are added in almost each release of the cart and are initialized properly when populated thru the sc ui.
I recommend a fresh install of the same version of the Cart you are running now (4.67) on a clean install of DNN and use the instructions above to export then import your data. Once the data has been moved, then you can go ahead with the upgrade which should properly initialize any new fields.
Both the data backup and import as well as clean install with data backup instructions are outlined in the following forum post:
http://www.smith-consulting.com/Forum...
We can also migrate the store data for you if you purchase the Module Upgrade Service located at the following link -
https://www.smith-consulting.com/pd/P...
Important: When upgrading, it is always recommended that you first do the upgrade in a test environment and make sure you have a full backup before installing on your live site in case you need to rollback.
Hope this helps!