To replace the hammer spring is really quite simple on a Sig. Take the grips off, then cock the hammer (of an empty gun of course) and notice the little hole in the strut around which the spring is mounted. Put a straightened paper clip into the hole and decock the hammer. The strut will be loose then. To put the new spring on the strut, use a clamp to hold the strut while you slide the spring on and compress it enough to get the paper clip back into the hole, then set it in place and cock the hammer then remove the paper clip. Easy fix for heavy hammer springs.
Thanks. I might YouTube it if it is that easy.