Wow!! What kinda sound did this make when she locked up on you ... I would go with a rebuilt, but most places require you to have a core to exchange with. Is it just the bottom case that blew apart?
I don't know what it sounded like as my kid was riding it.
It is both the bottom and top case plus then the counterbalancer and the crank. I am looking at a couple of used engines that I would most likely still do a top end rebuild at least. We will see.