I'm sure some poor watchmaker was rolling in his grave when I was using his tools and breaking the mainspring with my ham-handed attempt at fitting the eye closer to the arbor.

It broke at the hole that attaches to the arbor. Can that be repaired or is it toast?

I've actually repaired one using the method from the Fried book for the end that attaches to the barrel, but I think I read somewhere that if the eye breaks then you shouldn't repair that and just get a new one. But they don't grow on trees, so I was hoping to fix it.

Dale,

The short answer is yes it can be done.
Is it a good repair or good practice? No, if the old brown steel springs are worn, damage or compressed you are better changing where possible.
the white alloy springs are often good for re use.