I'd cut that mess all the way back to the trunk. Build a new trellis and grow a new vine this summer. That will put you in ideal shape for a big crop in 2014. Then in the spring of 2015 you'll have the ideal situation to learn how to prune properly. It's not that hard unless you have plants like your current plant and you want to get things right without missing a crop. By missing one crop you will be ideally setup for annual pruning.

I love to prune grapes more than anything else because done right the plant looks the same every year after pruning. Everything else bets bigger every year and eventually needs renewal pruning, just what your vine needs now. Done every year it's easy. Done once in a while not so much.

Thank you so much fruitnut! I was wondering if I should cut it all the way back. I'm always afraid of pruning it all the way back. I can't imagine how it grows back when you cut it all the way back to the trunk, but I have to trust it, huh?

It's not possible to tell where the new growth will come from but I'd be 99.8% sure that it will. If it's up on the trunk, train those shoots up onto the new trellis. If it's from down by the ground train the strongest shoot up to the trellis, tip it, and run the side shoots down the trellis. Those new shoots will give you fruit next year.