I would suggest running a few simple, self-contained adventures before diving into something as long and complex as Rise of the Runelords. I also found the Core Rules a little daunting at first, which is what makes the Beginner Box such a great introduction.
You can download plenty of low-level adventure modules from the Paizo site, which can be adapted fairly easily to BB rules. I'd use them to get yourself and your players more accustomed to the basic rules before you attempt something as long and involved as RotRL.
And remember the bottom line is, have fun. If a rule isn't working for you, throw it out and improvise.
Just my two cents!