Actually, is it a flathead or OHV motor? Flathead is way easier - OHV will be a pain , as youd have to pull the rockers, change the headgasket, ect.
Usually a good rule of thumb for me is to put a tiny dab of never seize on the threads of the plug, to prevent cross threading- its best to hand tighten in, then use the ratchet to finish tightening.