I have done all of this before for different dropship customers.
I have placed orders on amazon, walmart, kmart, toysrus, ebay, abebooks. Used woocommerce, shopify, salesfreak as well. Kindly share more details. I have also maintained accounts, used credit cards, paypal, excel sheets. Helped with customer support regarding orders, shipping, return, refunds and more similar tasks.
Looking forward to your response.