How difficult is the test?
Should I take classes prior to taking the test or is experience making 1 project good enough?

It really depends on the complexity of your one project. The basic class covers some less-used features (although once you learn about them, you use them more often!). These features may be included in the exam.

I personally got quite a bit out of the course. If nothing else, it introduces you to IA staff that you'll rely on later when things go wrong. You also get a glimpse into their world and understand the product dev cycles and upcoming features better.

Yeah it really depends on how broadly your one project covered the features of Ignition.

classes really sound like a good idea, How much fun can you have in Cali while you take the class?
What are the hours like on these classes?

There is a ton of stuff to do in northern California. The class hours are from 9am - 4pm Monday - Thursday and 9am - 12pm on Friday.

Here are a list of classes with dates:

http://inductiveautomation.com/events