Wow that's a shame. Hopefully someone will know how much work it is to fix yourself. It would be a shame to have to send it off to S&W and wait but you DO want it done right, especially anything regarding the safety and decocker. Any good gunsmiths nearby?
Again, I hope someone here will have more experience with the 59.
The biggest issue with assembling an AR isn't so much getting the parts together right - it's getting the right parts together.
You'll remember the quality of a gun long after you forget how much you paid for it.
US Army 1966-69, VFW Life Member, Retired Geek