Sexing is harder than it looks, but like many things once you get it down it's no problem at all. The best thing you could do is find someone local to you and have them show you how in person. If you can't find anyone local then online videos are going to be your best bet. (Justin Kobylka has a youtube channel that has a bunch of great videos on it. Including one on sexing)
Improper sexing can permanently damage/injure a BP. Both popping and probing are risky, but I think that the general consensus is that probing is more dangerous than popping is.