Hi Lucie, sorry, this is the iPod Community, there are no clever Apple people here, they all busy selling iPads, but there are a few smart iPod users here, so dont be dishearten if our suggestions dont work. Try the Genius at Apple store.
Being not so smart, I need some clarification on your problem.
When you mentioned
I think the library is just corrupted, but i have no way of fixing it. i
Are you referring to the iTunes library? if not then hopefully your iTunes library have all your music. Your problem is the iPod hardisk, which is dying.
Do the iPod DiskDiagnostic as posted by tt2, it wont fix your problem but helps in troubleshooting.