If you trailer for any distance, you may want to buy an extra set of bearings, bearing race and seals to carry with you just in case.
If you have Les Schwab do it for you, the crew there will probably let you watch them do it so if your bearings go out on the road, you can replace them yourself. The only real thing to be careful of is not tightening the main nut too tight or too lose so your bearings can spin freely without any wobble or binding. Don't forget the cotter pin.