1st remove sail loosen backstay and slack rig slightly uppers mostly. on the bow (pull boat bow in at dock ) if in water hang the umbrella trick or put your ding on front boat to catch anything. pull jib and spin halyards real tight on nose and pull main haylard down too. remove the original...
I had one like that rotten in places dug out rot and just used what's left as core and remade in place with glass and mat probably spent more than cutting out but now it's all white and no way it could rot again as its 60% glass
Remove mounts one at a time and note any shims under them set new next to old on flat surface and using a small level set up to match existing settings. if new style doesn't adjust to same heights then you made a bad choice
That purple line looks questionable to me almost looks like a hardware store line. Yea cut 4" off and check core if there's not another brade of rope under there move to garage as a handy tie stuff up rope in back truck or something other than boat