It's hard to say what you should do.... 60CT are pretty inexpensive now. It's entirely possible your problem is something easily and cheaply fixable but that's only true if you can do it yourself. Having it professionally looked at and getting it repaired will likely far exceed it's replacement cost. Plus, if you are not familiar with electronics, high voltage circuit like flash guns aren't something that should be your first attempt. It may not kill you but it can hurt you.
No, voltmeter won't help you. Unless it's REALLY dead, most batteries will show full voltage with no load.