'fixing' a waist isn't difficult if you are pretty good at sewing and have had lots of practice. If you don't you may want to consider taking it to a place that does wedding dress alterations and having them fix it. They are typically good with delicate fabrics and can have it done in no time at really minimal cost.

If you do it the wrong way and really don't know what you are doing you run the risk of destroying your dress. In the long run is it really worth $20 to risk ruining a dress that I'm going to assume cost you thousands of dollars?