Start with the FAQ and then read shadow's post.

1) 20-30 buyin downswings are very common, 45ish is not unheard of... but overall variance is lower than in cash games
2) There's a program floating around that can simulate this based on your stats.
3) Never posted a losing month.
4) After 1000 games you should know if you are playing winning poker, but your ROI still wont be very accurate until you play a few thousand more.

Also, don't start at the 55s. Start at the $22s and $33s for a month until you've got your game down.

Again, read the FAQ.