I'd definitely try a drop of oil before looking into replacing them. If it was a nylon string I'd also recommend rubbing plain soap on the string rollers to give them a bit of lubrication against the wood (doesn't apply to you but I thought I'd mention it in case anyone's having trouble with their nylon string tuners).

It is nice to put a fresh set on an old guitar though, and you don't need to spend that much. Schallers are good.