that depends on what you are wanting to do. the upper arms are easily rebuildable as all the parts are available. the lower arm you can easily replace the bushing, but to replace the ball joint, of which there is no factory type replacement available, is much harder. you can however install a screw in ball joint, opentracker has a kit to do just that as i recall. if you are just doing a stock rebuild, spend the money and buy new upper and lower arms and be done with it.
The upper can be rebuilt, but Ive never seen the lower in any form other than a complete control arm. For like $45, its not worth the trouble of rebuilding a lower anyway. Unless youre customizing (roller bearings, reinforced, etc.), just buy them already done.