It's like many other training situations you may have been in -- high school two-a-days, military boot camp, fraternity hell week -- where the group gets broken down at first, then you find strength in making it to the end. Most of the battle is mental at first, because like BTO said, the first 2-3 weeks you hurt a lot. It does get much better after that.
A lot of people will screw up somehow and earn a nickname, and EVERYbody will get singled out at least once early on for screwing something up. And although it goes against my nature, I found the best tactic is probably just to do what they say, keep your head down and get through it at first without being a smartass. You'll get through a lot smoother that way.
You'll be glad you did it. I ran my fastest 5k in like 10 years after the training, and we never even ran distance in the class. I think the most we ever ran was a mile, maybe mile and a half. You just get stronger physically in every way, and that includes your lung capacity.
Plus, the ladies love it, ifyouknowwhati'mtalkingbout.