If the starter works you probably need a starter drive to change the drive you will have to pull the starter out .then you will see 2 bolts on the back of the starter takke them out and remove the front nose cone the drive is what slides on the shaft ..there is a plastic cover covering the o ring remove plastic cover and o ring drive will slide right off.but it would be just as easy to replace starter
replace both starter and selonoid as one unit. New. at any auto parts store. You may have to pay a core charge which you will get back when you return the old one. Or try the Internet, Rock auto has good prices and fast delivery times.