Via messenger is not the best way, you should use Justin.tv or Ustream. I like justin.tv because you can have the broadcast automatically recorded. If your camcorder is a digital camcorder it can work and will be better quality than a webcam. If not, you would need to buy something that allows a composite hook up to the laptop, probably a TV card, to stream from the camcorder. The most important thing is to do a few test runs before the actual event to make sure it works.
Let me know if you need my help with anything, I've done this sort of thing before.
