ARoarer, on the top line of your post, over towards the right, there is a little button that looks like a little sheet of paper with a pencil at the lower right corner. If you move your cursor over it, a little pop-up window should appear that says "Edit Reply". Push the button and you'll get an editing window to come up. It's just like a regular reply window, but it contains your post. Make the changes you want, then press the "Resubmit" button.
AlanF