We use full product sync on farapp, although I've never switched from price/qty to full sync.
What I would do is to turn off syncing for products temporarily in Netsuite - change the shopify flag on items to 'ignore' or something and keep one test product active while you're editing sync. Then add fields one at a time to the field mapping on products. It takes quite awhile to get field mapping all set up and debugged in full product sync. You can basically re-create price/quantity sync inside of a full product sync by only mapping those two fields. After you've got something basic set up in the field mapping, start re-syncing the products by switching their flag back to 'add/update'.
As long as the key that you use to sync items to shopify (for us it's the sku) doesn't change, and as long as you don't flag the items to be removed, you should be fine.