Hello all, in talking about mainsprings [200813 MMD], Jody remarked
he is not brave enough to tame those ugly ones!  I'm sure he is right
-- please make sure to take any safety precautions you can imagine
before going into any risk.

An article in DMM 133 may be helpful even if you don't want to
translate the text; the pictures are self-explanatory and show some
tools and tricks on how to proceed:

https://www.musica-mechanica.de/media/PDF/Aufzugsfeder_gebrochen.pdf 

Regards,
Uwe Gernert