My 2004 Kawasaki Vulcan 800 started sounding like a locomotive @ 16K. what could it be?

I recently started riding; about 1000 miles after I took the bike in for her 15,000 mile tune-up, she started sounding like a train. clank-scrape, clank-scrape, clank-scrape. In idle she's fine, but once I put her in gear and start rolling the sound starts up and speeds up as I shift. I stopped driving her after the first day in fear that I would cause more damage.
Does anyone out there know what it is, how I can fix it myself - I am mechanically inclined - or how much it would cost, on average, if I were to take her in?