Odds of Getting In
First and foremost, you need to know trains. As the person responsible for all of the onboard happenings, you really need to know your engine from your caboose.
Even if you're perfect, the big hiccup here is that railroad jobs are predicted to decline over the coming years (source). Trains are becoming more efficient, which is kind of bad news for the guys who benefit from more trains zooming back and forth across the country.
On the bright side, a lot of old-timers are expected to be retiring over the coming decade, so they'll need plenty of fresh-faced recruits to take over. Looks like all that time you spent watching Thomas the Tank Engine is finally going to pay off.