No quick answers, other then there are few jobs, and many, many people competing for them - there is no one road there. Usually a General Manager is looking for someone who has experience on Broadway already. (There is a challange).
When I was in New York, I found that my regional theater experience would get me an interview here and there; it was not until my last week in New York I got four interviews - yeah, all with in two days of each other - and finally got one firm offer. I turned it down for a host of reasons.
One way is to get in early to the whole commericial scene, as a PA and work yourself up. (Hard, though, many people find it hard to jump from PA to ASM).
Move to New York, work on off-broadway shows, and hope for an opening.
Network, network, network.
Do a show that transfers to Broadway.
Lots of ways, not one is a "for sure" method.
So to answer the first question, not easy at all - not easy at all.