Yeah, not sure if you are talking about front or rear here.
The fronts are definitely more difficult, as the bearing and hub/spindle must both be carefully pressed into the knuckle.
When I was racing the SC2 and replacing bearings often, I bought an extra set of front knuckles and paid someone else to press in the hubs and bearings. Then I carried around an extra set of complete ready to install front knuckles. This made it possible to do at the track with simple tools - though you will need to guestimate an alignment afterward.
The rears, on the other hand, are quite easy - because the entire bearing/hub/spindle assembly bolts on and off from the knuckle.
For the rears, just follow these instructions for the rear hub spacer
http://www.spswebpage.com/Installation-Instructions/Installation-Instructions-for-Rear-Hub-Spacers.html
Just ignore the parts about inserting the spacers.