Sync Amazon Seller Central/Zen Cart Stock List

We sell the same items on Amazon Seller Central as our Zen Cart powered database. The stock list contained in our zen cart database is considered the master stock list. We need someone to sync our Amazon sales to our Zen Cart stock list to fulfil the following criteria: We have a text file containing Amazon merchant SKUs and the Zen cart product IDs like this: SKU: Zen Cart ID: AS-FHRW-FJAL 419 1) An item sells on Amazon - reduce the Zen Cart stock figure by quantity sold 2) Item qty in Zen Cart <= 0, end seller central listing 3) For an ended seller central listing, if zen cart stock =>1, relist the item on Amazon with qty 100. The script will be run on a cron in order to update stock levels throughout the day. We can't allow access to our ZC database or Amazon account, so you will be expected to run it on a demo server/accounts and we'll install it on our own server ourselves. Give me a realistic estimate of completion time and make sure you can do the whole job. We have lots of projects on the go, so there could easily be more work for talented people.