I am happy to see this thread, and to know that someone else feels the way that I do. I'm not 40, but this is going to be my second wedding, but fiance's first. I was feeling akward about everything at first, but then you know what... I do want a wonderful wedding. (and not to mention that I didn't plan even one detail for my first wedding... didn't even get to pick the dress)
Bottom line is, don't feel akward or too old or anything else. You deserve to have a wedding day that you can smile back on. If you would rather wear jeans, do it, or if you dream of Cinderella's ball gown, wear that!
It's all about you and the love you will share with your spouse that day.