How long have you owned it? If it's 2002 and you don't know the bearing service history, than it's way over due IMO..
My trailer is a 2003 and I've owned it since new and have done the bearings at least every other year and they may not need it each time, but checking them out and adjusting the brakes is always a good thing too.. ;)
If you have never done wheel bearings before, you need to learn it from someone that has done it before to show you how it's done.. There are tons of youtube vids on it, but until you do it yourself, and can feel how it's done... Well, I don't know? I was very lucky and my Dad showed me how to do this service when I was a kid and I've never had a wheel bearing failure..
Good luck!
MItch