There are aftermarket options to replace the pressed in ball joints. Nissan doesn't off just the ball joints, recommending that the entire control arm be replaced. My preference is to replace the entire control arm. As mentioned, you may have to cut the control arm bolts, if they are seized to the bushing sleeves. However, if you replace just the ball joint, you still have to do an alignment, and if the bolts are seized, you're going to have to cut them out, anyway, and then replace the control arm bushings, so adjustments can be made.