It doesn't hurt to call back just to check how everything is going. But, generally around (and during) the holidays, it can get kind of backed up. So, I wouldn't worry too much. :pCongrats, by the way!
I had the one day orientation about a month after I was hired and I didn't get to start working until almost 2 months after I was hired. I was hired a few months before the holidays in 2012 and it took quite a while to get my employee number so I could start working. Just hang in there! (:
Wear all clothes that's in style right now (all black!) also wear a full face of makeup that either is or looks like MAC makeup. If you have any specific questions, feel free to PM me! I've been at MAC for a year and a half now~