It's docking dependent steel work, but frankly a lot easier than the extent of the repairs we routinely do during dockings, as the scope would be planned ahead. The only tricky bit would be figuring out how much of the skin to take off the double hull to get the plating into tanks, and making sure you don't pull off so much the ship strength is compromised. Normal access is only via small tank openings, so pretty normal to cut access holes for tank work for schedule, and cheaper than trying to get it in via the 2'-3' access hatch that's 4 decks down in the ship (which is too small for any of this anyway).
That's normal for repairs as well, as some equipment doesn't actually have removal routes, but generally that's things like huge engine blocks or very large air flasks. Those are expected to have a similar lifespan to the ship, barring catastrophic failures (which is why maintenance is important), but the kind of thing you would like at doing as part of a lifespan extension.
Usually the killer part of all those jobs is interference items in the way that need to be pulled out, especially anything with power connections, or wire routing along the way where you need to disconnect it (with LOTO and tracking, so it gets reconnected). There really is nothing in the tanks, and pretty minimal stuff in the double hull (if anything) so it's almost exclusively steel work and painting. So time consuming but not difficult.
