Q: Click wheel is totally unresponsive even after restarting & flipping the hold switch on & off

You can work through the remaining five 5 R's of troubleshooting.

http://www.apple.com/support/ipod/five_rs/

It might also be a good idea to let the iPod's battery fully drain. Then charge it back up and restore it once more in iTunes.

Otherwise, it's likely a hardware issue with the iPod's clickwheel, meaning you'll need to take or send your iPod in for service either via Apple or a third party repair service. Here is Apple's repair pricing.

http://www.apple.com/support/ipod/service/prices/

Note that they don't actually repair the device, but exchange it for one of the same generation, model, and capacity.  A third party service will actually replace the damage part for a little less.  Google "iPod repair" and you should get a number of results to work with.

B-rock