Time to dress up? Might be just the time to do a Google search for the tricky bits. Hannah had a long, gorgeous teal sash to go with her wedding dress and after a few failed attempts, her mom went online to google the process… a few minutes later, they were able to finish the sash and fine tune the bow in the back. Aria offers a few sash styles to choose from.
I ran into this same situation a few years back with a group of groomsmen… a bow-tie can be a pretty foreign concept these days and a Google search offers several really good guides for working with just about any style of tie. The Art of Manliness is a good place to start for various dressing tips.
Personally, I think you should do the homework ahead of the wedding day so that you can avoid that sinking feeling as you realize that time is running short. ;0)
Get dressed and have fun!