You posted to the wrong forum, but I am familiar with swing keel / centerboards.
Of course you will need to haul out first, then locate the bronze center pin which holds the centerboard in the cavity. It will likely have bronze retaining blocks which are cast & faired into the hull at the forward end of the keel at the pivot point. But you may not have to remove the center board to repair the crank & wire. Usually its the o ring that attaches the wire to the end to the centerboard that corrodes away & finally fails. You will have to tap & thread in a new eyelet type ring which is 316 Stainless steel or better to help prolong its life against corrosion. Morgan is of course out of business, but Catalina used a lot of swing keel parts in the C 25 which are similar in design. The crank assemblies were usually just an afterthought, & used tackles similar to that of a trailer crank & they suffer from rust corrosion, badly over time. Also find the best quality s.s. cable that you can buy, such as that used for heavy stays & shrouds from a rigging shop. Good luck.