i wouldnt change regulator if it hasnt failed. just unsolder the brushes out of it and replace. is a bearing at either end of the rotor that can be done.be careful removing bearings and try not to lever off other parts etc and use a press if possible. make sure the slipring hasnt got a big groove where the brushes run. but really an alternator nearly never would leave you stranded on an overpass. you will almost always get warning light, nasty noises or electronics will start cutting in and out before you get stuck.