I do mine myself but then I have done lots of bearing repacks. If you have to ask how it is done, I would find an experienced friend and have them show you what to do so you can do it next time. It is not very difficult (although it can be time consuming) but there is definately some tricks to repacking bearings by hand. I do mine every couple of years but then I don't travel full time like some do.
Or....you can spend your time golfing and let a mechanic do it for $100.00 or so.