Get a Haynes manual. Then go to RadioShack and get a digital multimeter. You can try to fix this yourself :).
It sounds like something's dodgy w/the charging system... from memory (sorry, I don't have my Haynes manual handy), here's what I'd do:
-- get multimeter.
-- take off seats so you have direct access to the battery.
-- CHECK ALL CONNECTIONS to the battery. (Sometimes the obvious is overlooked!) Check your fuses while you're at it.
-- measure the voltage at the battery. It should be @12v-ish.
-- start the bike.
-- measure the voltage at the battery. W/the bike running at idle, it should be @13.5v.
-- run the idle up to 5000rpm and measure again. It should be btwn 13.5v and 15v.
If the voltage is out of range, suspect the voltage regulator. In my experience, alternators don't go out very often, and voltage regulator/rectifiers DO go out. The voltage reg/rect is an easy thing to replace (but we'll jump off that bridge when we get to it!).
Let us know how you get on w/that, and we'll go from there.
"I believe what I said yesterday. I don't know what I said, but I know what I think, and, well, I assume it's what I said." - Donald Rumsfeld