If this is on a 3G/3GS you will probably want to order a new glass/digitizer while you're at it. You'll have to remove the glass from the plastic mid-frame in order to remove the home button.
You may be able to take the glass off without any problems, but it wouldn't hurt to have an extra in case it cracks. If you are careful & end up getting it off without any damage, well then you just have an extra in case you ever drop it & break it.
For $8-9 the extra insurance can't hurt.