Very much depends on why it seized. Does the piston still turn now that it's cool'd down? You'r going to have to tear it down to find out. Waaaaay too much could be wrong, some things are repairable and some turn the motor to junk.
I have a 49cc that's never run:bad magneto coil, that I was going to list in the yardsale section but I'll give you first shot at it for $50 shipped. It will need the magneto coil and bucking bar in the clutch from your old motor but like I said, I bolted it to my frame and tried to get it to fire. Ran the tests and discovered it was the magneto coil. I'll even send it with a NGK B6HS installed, well, in the box.
I have a 66 cc I'll be selling, too, but it has major bolt-ons. There are ...."things" on it unavalible from anyone. That one I will have to list in the yard sale. So many up-grades the sum of the parts way exceeds the cost of the motor. I'll be listing it at about 50% of what I have into it.