craftgrrl | Dress conversion issue?

Hello ladies. I have an interesting project that will be commencing in about 2-3 hours, when I get off work, and was wondering if any of you fabulous crafty folks had any suggestions.

Here's the deal--> I'm going to a formal event tonight (fancy-pants fundraiser) and need something formal to wear. I don't have any fancy dresses, but I do have a really nice black top. I also can't just go out and buy a ball skirt because (a) they are expensive and (b) I am really tall so they always end up too short. So, I decided to make a ball skirt. Rather than buy all the material and stuff, I decided to buy a dress from a thrift store and just cut off the top. I found a lovely (albeit too big) empire waisted dress that would be perfect (I needed an empire waist dress so that I can make the waist higher and therefore the skirt will be longer).

Any hints on how I should go about doing this? I plan on cutting off the top of the dress just under the empire waistline, and then hemming the top and adding some elastic inside and a waistband of some sort. The dress-soon-to-be-skirt is a maroon color and my top is black. There's a zipper up that back that will remain in part.

This will be my biggest project to date, and of course, it needs to be done by this evening! Ack! Please help! Design ideas, practical ideas (how to make a waistband?), and any other ideas are all welcome. Thanks!