I have built an entire Dropshipping System before for an ERP called NetSuite, so I already know the concepts and pitfalls. Also I have broad experince with Amazon MWS API which we can use partially, along with some web automation (and scraping).
I think the best way to do this is using an integration platform, it costs $4500 USD. I can make a price for you for $3000 USD. Then you can use the same platform for other web scraping, automation or integration projects you need.