Hello,
I had done some import task of products from another third party websites to shopify over their API. They are such as Bonanza, Amazon, Quickbooks Online, or any other dropshipper services. They are wrapped into either cron/scheduler task, manual trigger, webhooks, etc.
Let me know what logic flow you prefer to implement regarding to Shopify sync. We could use the trial account for this purpose, so it won't break your currently running shop.
Three days would be fine, but in case you provide a clearly instruction, two days or Sunday evening you will have it ready.
Let me know your feedback.
Regards,
Khamid