It is not a problem to do only the ball joints. Either use a ball joint splitter or slacken the castle nut and whack it upwards with a hammer to split the ball joint. Remove the circlip from underneath the balljoint, turn the arm upside down and whack out the balljoint with a hammer. To put the new balljoint in, remove the balljoint rubber boot, place a large socket under the arm and hammer in the new balljoint, fit the boot back on and place the new circlip. Fit the arm and jobs a good 'un
Make sure that the new balljoint fits well and does not rattle up and down. I have experienced this with new aftermarket balljoints before.