I can do it myself easily now, but the first time, I got my piercer to change it from a CBR to a barbell.
If you want to try and do it yourself, just hold the ring with one hand and push the bead out (or hold the ring with 2 fingers and use your thumb to push it out, like I do). It'll probably be quite tight though, piercers always seem to screw on the balls or tighten the ring so much that it's impossible to get out :P