my experience here is to go to trailor places for that (places that build, sell, rent and repair all kinds of trailors)......on a one axle trailor it is $65 to $70.....for that, they replace bearings and seals....they told me that it was not profitable to take the time to clean and inspect the old bearings....just put in new ones.....they are just too cheap and no risk that a bad bearing could be overlooked....if you have ever been stuck on the side of the road with a bad bearing at 10 at night you will always remember to pamper your bearings.....$$$$$$ well spent.......my new boat has the oil bath and I have brakes.....seems like those systems have problems with leaky seals.....just had a seal replaced and oil changed out for $120.....

good luck