Usually the valve seat can be re used either a new valve and lapping, but they can just cut the seat, even just one if that's all that's needed.
I can usually find those heads pretty cheap on FaceBook.
You need an inside telescopic bore gauge to check the cylinder, yes they often look nice, but the cross hatching will be all gone aside from where the piston rides.
If it's that worn and the seat is toast, how is the cam, rocker shafts and rocker pads?? Those are all hard to find new
parts but lots of use ones out there.
I probably have a good head I'd sell after you get an idea of a cost on your
parts and see what will work for your wallet.
Do it once and do it right, keep it filled with oil and warm it up properly. It will last your forever...
Biggest issue I find with motors is a lack of changing the oil, and running low on oil, that's what ruins these otherwise bulletproof powerplants.