I'd be looking CLOSE at the top of piston if not replacing it. I've seen banged up pistons go back in and run fine, but always the possibility of pieces of cracked ring land coming loose later to screw things up. Better to change piston. Seems you may have been already going in that direction............
If yanking the one then not that much harder to yank others to change ALL rings, my concern would be the TTY rod bolts, if motor uses them then the rod bolts are one time use only. Meaning if you break them loose you should be changing them. All adding more cost of course.
I believe you can do it without yanking motor, many times that's a personal preference thing, do you mind oil dripping on you for a bit? It'd save a lot of work. Retiming cam may suck since can't see in there too well. Change water pump for sure, it'd be ridiculous to fix motor and next week water pump fails and bends all valves when it locks up the belt.
Not totally necessary to change all rings, car owner I'm sure would be happy just to get a running car back. You'll get back some pep by going over the exhaust valveseats while head off, or valvejob on new head. The valves (especially exhausts) generally leak more over time than the rings.