[JamesMio]

I think a cheap wee Multi-Meter would do the job.

As far as changing the regulator/rectifier goes, it's not a difficult job - literally a case of a few bolts to remove the rear plastics, grab rail and pop out the pillion seat lock cable, and the regulator's as others have said bolted onto the right hand side of the frame under the rear pod. Two bolts and it's off.

PS - do you have a Haynes manual? Worth their weight in gold for stuff like this...