[ame=http://www.vimeo.com/1669341]Change 3rd Gen iPod Headphone Jack on Vimeo[/ame]

You can get some iPod 3rd Gen parts here:
iPod Parts / Installation - iPod 3rd Gen - ifixipodsfast.com iPod Repair / Parts
3G iPOD PARTS: RapidRepair
iPodParts.com is the iPod Parts, iPod Battery and iPod Parts Repair Value Choice
iPod 3rd Gen Parts - iFixit
3G iPod Parts

If you need some help post up!