A Job?

So I was offered a paralegal position today at a large law firm with training to begin in a few weeks. The problem is, I have a second interview for the job I really want on Wednesday. I asked the law firm if they could hold off until the end of this week or early next week for an answer. They're going to try to hold off that long but I am taking a gamble. If I don't get my top choice job, there is a chance I might already have been replaced at the law firm. So, I'm making a bit of a risky move, but I feel like it's what I need to do. In any case, it seems like I'm going to be entering the working world very soon.