eBay Listing Program Using Amazon API

I need a desktop application that is usable across windows and mac and is easy to install and use. I don't care what language it is programmed in as long as it meets the requirements. One option that has been proposed is node-webkit. The goal of this application is to enable users to create and manage eBay listings in csv format using Amazon product information to create the listings. This is the basic summary of how it should work: 1) There shall be a GUI where the user can input their Amazon AWS credentials as well as set initial eBay listing options 2) Once the ebay lisitng options are set the user then uploads a Amazon ASIN csv file that contains a list of ASIN codes and eBay category id numbers 3) A script will run that takes the ASIN codes from the upload file and runs it through the Amazon Prod Advertising API and returns listing information such as title, description, pic url, features, price, etc for each item. This information is then formatted into a csv export file that eBay file exchange will accept (will provide format required) whereby users can upload to their store. 4) Once the listings are uploaded to eBay the user will be able to download their active ebay listings via file exchange and use the ASIN codes from that file to manage their listings on a daily basis by obtaining recent prices and availability through the Amazon API. They will load an update file to eBay file exchange each day to manage their lisitngs. 5) There is also a screen where the user can lookup suggested eBay category id's in case they want to build their own ASIN upload files. I already have the code for this completed. Attached is a draft wireframe of what the GUI could look like along with notes on the functionality. I have a lot of the code already completed from a previous freelancers work on this project that covers most of the Amazon API part and the eBay Suggested Category feature. The main need for this project is having someone take the components and ideas i have already developed and build an application that anyone can use which works across Windows and Mac. Thanks