Custom eBay Helper Desktop GUI

I'm in need of a talented software developer experienced in creating desktop applications, API integration with eBay, and inventory management. The application will interface with aspects of my business (selling digital items) that are not typical for eBay, so off-the-shelf apps aren't capable of handling. It should be a standalone Windows app.

Key features you should be able to develop:
- Listing Quantity updates
-- Update my local inventory count as items sell
-- Pull from my local inventory files on demand and update quantities available on eBay accordingly
- Order Tracking
-- Alert on new orders
-- Identify repeat customers
-- Pull specific info from buyer note or buyer messages
-- Help with fulfillment by pointing to locations inventory is available (i.e. from local files)
-- Have a place to store images related to transaction
- Buyer Interaction
-- Function for sending and interacting with buyer messages integrated in the tool.
-- Templated messages with ability to add more

If bidding, please demonstrate you've read the brief by mentioning you know the project is about digital goods. Let me know of any experience in developing similar tools or applications. Proficiency in desktop application development is a must. Familiarity with the eBay platform and its API will greatly benefit the project.