If you have an older style speed sensor with the longer axle and the small circle clips on each end, the included axle will not work for you but normally your axle can be reused as long as it is still straight and the clips can be hammered flat and reused as well.
If your paddle wheel on your speed sensor has a broken lobe, this is what you need. Removal of your old paddle wheel is simple, 5 minute installation, youtube video below. Retail price is $58.99, get it here for much less.