It shows normal wear for it's age, not too bad really.
Yes it IS worth rebuilding they are good engines.
I'd say you got lucky, looks like the crank/rod lack of lube was what stopped it.
Honestly, it should be rebuilt, doing it properly,
not a "repair" of cleaning the crank up with acid and replacing just the rod.
the piston shows wear as does the rings, they don't owe anyone anything.
To do it right, it should have an oversize piston fitted as the bore might be egge shaped and tapered also the crank checked and ground undersize if out of speck, with corresponding undersize rod.
that said:
Ya you can deglaze the bore if, it is not scored( pic's are not clear), go new std piston with new rings and clean up the crank and replace the rod with new std.
it is cheap and down and dirty, that
I would not do.
But I get the idea it is just a play tractor????????
and you are not going to work it like a weekly mowing or fitting a garden/snow plowing.
just my take
Edit:
I see Finsruskw multiple finger typing, is faster than my one finger approach. :>)