Well is it a 2wd or a 4wd? I assume the bearing races are pressed into the rotor? You can beat them out with a stout heavy hammer and chisel. to install them you would need a bearing race installation tool, which is basically a handle that you hammer on, and various sized aluminum cups that fit into the concave bearing.(found this:
http://www.sorba.org/forum/viewtopic.php?t=23021 you can homebrew your tool)
(I had to replace the pinion bearing race in the rear end of my truck, same thing, except the bearing was larger in my case)
I've actually had never had to replace the spindle bearings, as the old races work just fine, and if I do get new rotors, they are already pressed in, pre assembled..