I have an interview this monday for an acting job?

honestly, i have never acted in my life. im not good with people. i have no confidence but i did see an ad for an acting gig in the newspaper and had the balls to call. The ad said they needed actors/extras for a big hollywood movie so i called and some guy told me to come in for an interview on monday. What should i expect, should i even go? im 21 btw