I understand your pain Spudly. There are pictures of me in hideous purple puffy dresses with my hair in strange do's to prove it. What we do for family and friends!
One time I forgot the dress and wore something near the same color and no one cared. It was pretty casual, like the one you're going to. All that preparation is such a drag. Think of an excuse not to go.
In college I took a radio/tv class and we had to act out commercials for other classmates. I had to totally let go of me and get into the part. I'm not into acting at all, but looking back at the videos is such a crack up, and it actually was fun. My advice is to be the best actress you can be.
You're a good friend. I hope you get some good memories out of it.