Aw, that sucks right before Thanksgiving. But at least you have an appointment right away to get it looked at. Most dentists are great at being able to analyze and fix the problem immediately. If the tooth wasn't bothering you before, more than likely a crown will be the solution (cheaper than root canal). They'll probably prepare the tooth today, take impressions for your permanent crown, and put a temporary crown on that will hold you right through Thanksgiving and longer. No worries :-)