Please help with job advice?

I had been job searching for over a year.It has been making me extremely depressed that i couldn't find the job. Yesterday, i had an interview. And to make a long story short, i got my first job. However, during the interview, the manager was talking about how important it is for people to not have many absences from work (obviously). So, i am going to be at work every day i am scheduled for. However, a couple of months ago, my aunt bought me a plane ticket to go to Mexico with her for ten days. Suprisingly enough those days are right in the middle of my December break, which means a potential work overload. So, i am nervous and i have no idea when to tell my manager, how to ask for those days off but show that i AM dependable. I have no idea what to say and i know lying is out of the question (though i considered it...surgery?) so HOW DO I TELL HER THAT I AM GOING TO BE GONE BUT STILL KEEP MY JOB?!?!?!