I have had my iPod nearly 5 years,a nd it has worked fine. Till today. I can still play music on it through speakers and the iPod itself. But it will not sync or allow me to add anything new. It's a waste of money getting Apple and their rip off repair price £126 to fix it.
But before I shell out money for a lower spec replacement is the unit dead totally?

Unit cannot be totally dead if you can still play music through it

I would simply download the latest version of I-Tunes and then restore, then try to re-sync.

Tried resetting it. It doesn't do anything, I even tried a different iPod cable in case that was the issue, even that didn't work.
It's bizarre as it will play music, it just will not sync.

Does it appear in iTunes?

I have one that has a tendancy to lock up completely. When that happens to mine, I take the back off, unplug the battery, wait 5 seconds and plug the battery in again. It then works perfectly for another couple of months.

Why oh why can't they fit a PROPER power switch to allow you to re boot it when it's crashed?

you could try unplugging the battery on yours to give it a hard reset.

You can do a hard reset by pressing down, and the centre button at the same time and holding for 10 seconds

Yes it appears in iTunes. I have tried it in several USB ports, and it does the same in each. The sync appears for about 4 or 5 seconds, Then it stops. I am thinking it's basically knackered apart from playing music. Shame as it means I cannot add anything new, ever.

NOT when the thing has totally locked up and appears to have crashed completely you can't. I've tried, and the ONLY way is unplug the battery, then it will start and operate fine for a few more months.