2 wheel drive front have pairs of old school tapered bearings that ride in the rotor.
Best bet is to buy new rotors (they usually have the races already pressed in), the tapered bearing sets, and some moly grease. Easy to replace, the hardest part is getting the preload right on the axle nut. It should *NOT* be tight (your bearings will melt), but it shouldn't be loose either (your wheel will wobble).
If your bearings are newish, and you don't see anything bad in the grease, you might try snugging the nut up first.