stripped driveshaft?

thanks for all the help. i definitely had it in my mind to make sure it's not the input shaftamabobby, since i've never pulled an engine before, i remember putting the outdrive on at the beginning of last year and thinking the teeth didn't look perfect. why would it definitely be the coupler and not the input shaft thingy? any idea what it should cost to have a marina do the work, parts and labor, if it is the coupler?