Minimum, you'll need access to the software suite, possibly firmware updates, and the hardware itself (or did the customer go eBay this?)

You should also know that Crestron has discontinued support for the application that sync'd the iPod while it was docked, largely defeating the benefits of having a 'permanent' iPod dock. I think it still works on older OS's (XP, Vista, Win7, OS10?), but since its not a product we used I'm not entirely sure what works and what doesn't.