Do it. Seriously. It won't be easy. At times it will be scary, dangerous, uncomfortable, boring, hot, cold, wet, dry, dusty, humid, etc. Shit will break. You'll figure out how to fix it. Buy something cheap, fully depreciated, and robust. 250 Ninja, GS500, EX500, KLR all come to mind. It will cost more than you expect, but you'll figure it out.
Learn how to do basic maintenance yourself. I mean really basic, like put air in the tires, adjust cables, lube chain, change the oil (you should only need to do that once), etc. Get Ironbutt - who posted earlier in this thread - to show you the basics (I just volunteered you, Chad!

)
Get a copy of Lightweight, Unsupported Motorcycle Touring for Terminal Cases from
Aerostich. Read it. Carry it with you. It's small.
Log into
Horizons Unlimited and read the stories for inspiration. Lots of folks over there have stories that go along the line of "passed my test and rode to Capetown", or "passed my test and rode to Peru". Read about Sam Manicom, or Tiffany Coates, people who passed their tests, then promptly embarked on adventure.
Get some used gear, and maybe a cheap helmet. Fuck the naysayers. Seriously. You'll have stories to tell for the rest of your life. Adventures, rescues, guardian angels, free beers, great scenery. And you will have done something most people, and apparently most motorcyclists are too chickenshit to try.