it's totally a woman by woman experience. some women experience little or no pain and others experience a significant amount of pain.
not to generalize too much, but probably i would expect a fair amount of pain (nothing you can't handle). if it gets too much for you then just stop doing it for a while.
you need to take your time, and just do it at your own pace. it helps if you control how much penetration takes place. you can control it by being on top for example, or just by communicating to him what he needs to do or just by putting your hands on his hips and pulling him or pushing him dependent on how you're feeling.
the thing is that this IS all about you, so when the time is right for you, you should own it and make it an awesome experience.
good luck!
jasmine