I replaced one ,a "straining type?" bronze thru hull, after bumping it on a rock on super low tide at ramp in GRiver.
Very simple especially with good access and done on the trailer...very little mechanical skill needed.
Unhook hose clamp,take handle off,ground wire (if equipped) back the large nut off,remove screws from outside under side of hull
Work the stem back and forth(you might need to use a knife to cut/loosen sealant on both inside and underside of hull..you should then be able to just push it back out through hull.
Install is just the reverse with the application of sealant of your choice before you install in hole of hull