[Yosemite Sam]

The short answer is, it would be difficult at best to Heli-coil it with the engine in the tractor.

You can take the engine out and then Heli-coil it. Good choice.

You can replace the pan with a cast iron one, and then FORGET about it. Better Choice.

FWIW, if you get your new pan and clean it up so that it suites you, a new gasket, and your oil, you can do this job in an afternoon. You can actually do this job in a morning and be driving your Cub later that day.