I would probably replace it if it's still under warranty, if not talk to a WD representative and ask them if it warrants concerns. I have one WD that does make a little noise and doesn't seek well but it runs just fine for me. I have a couple of other drives that makes the same noise but works just fine. I'd be more concerned with checking the S.M.A.R.T. settings and run some diagnostic tools on the drive to see if it's functioning well.
But like i said, if it's still under warranty and can be replaced, i would just do that. Just make sure to back up any data off that drive!