I want to replace a large section of the galvanized pipes in my 70
year-old house. I'm comfortable with all aspects of the project except
I've never used a pipe threader.

I have easy access to the galvanized pipe after it comes into the
basement (there's no meter). There's two joints where I can start the
new piping (with a di-electric union). The plan is to start with the
more distal joint and hope it comes apart without breaking. If it
breaks, then I'll go to the more proximal joint (and pray). If that
piece breaks, I'll have to learn to use a pipe threader (which I can
rent).

So my question: How difficult is pipe threading? How likely is
70-year-old pipe to stand up to pipe threading? What's the best way to
cut pipe before threading?

Would anyone recommend changes to the plan?

Thanks,
Mike