I have a steam radiator that I want to move a couple of feet. All the
pipe is exposed in the basement. I have a 24" wrench and a 36" wrench.
IF I can loosen the pipe, all is well. One guy at the local supply
shop said that it's likely that If I just smack the fittings with a
hammer, they'll break right off, but I don't know about that.

So, what if it doesn't go well? What if I have to cut the pipe off? I
know I can use a Dresser coupling, but the local guy says they're over
a hundred bucks. Is there a good internet source for those things? Is
there some sort of expanding plug that could go into a 1" steam pipe
to temporarily seal it so I can still have heat in the rest of the
house while dealing with this?

This stuff has been screwed together for either 60 or 90 years. Would
some sort of penetrating oil maybe help?

I know I could hire someone to do this, but I'm up for an adventure.

Thanks.