Hey wedding photographers, a little assistance please?

So my best friend is getting married this weekend and her photographer for the wedding just cancelled on her. Guess who just got pressed into service as a wedding photographer? As someone who is fond of neither weddings nor shooting portraits (I'm a nature photographer, dammit!) I've avoided anything to do with this particular kind of photography and now find myself in somewhat unfamiliar territory. Do any of y'all that shoot weddings have any hints, tips, suggestions, do's/don'ts, etc? Any help would be much appreciated!

Did I mention I'm also officiating the wedding? This is going to be an interesting weekend...