Automated Winding Mechanism

I need help designing and building an automatic winding mechanism. Overview Diagram: [login to view URL] I need someone to design and build the parts in the gray circle ie winding mechanism, control unit, computer interface and computer software. Ideally, I'd like to take delivery of this mount the winding mechanism, attach my cord, plugin it into my computer (linux) and then just be able to run the commands to automatically raise and lower it. It needs to be made of off-the-shelf products that I could buy myself (should I need spares or repairs). You will need to provide a list of components and some design/build diagrams and documentation and then ship the completed unit to me - perhaps after Skype demonstration. I think in practical terms the computer interface is probably going to be easiest/cheapest via a cable (preferred ethernet or serial, lastly USB) so please quote on that design. However, I would be interested in a Wifi interface (where the control unit connects to an existing Wifi network), so in the text of your response please estimate the cost of upgrading to a Wifi interface. I'm thinking something along the lines of a stepper motor with an arduino controller and an ethernet interface with a command line C program to raise and lower it between the limits. Your response should include a high level proposal for how you see this working. I may have not covered everything you need to know in this project specification so please ask. It is possible that this specification is far to open to interpretation so I may need to modify it based on the proposals I receive. Thanks