All of the people with enough knowledge to work on ,fix ,build any gun out there usually keep to themselves and don't work for major gunshops. Last AK I built was probably back in 2013 , last bolt action around the same time. I restored a sweet 16 back in 2014 with fresh hot caustic bluing for a fraction of what it would normally cost just because no one wants that type of restoration anymore with cerakote being the rage.
Anyone can swap parts on an AR style rifle these days albeit few do it correctly and have gauges to check tolerances and headspace ect but still. Now days no one wants to spend thousands restoring guns or building new ones when they can buy a "just as good" PSA or remington off the shelf. Call any shop that offers gunsmith work most will ask you to bring gun in but they can't guarantee they can fix it unless it's an AR or simple part swap.
I think buhler ballistics is still working on guns he might offer everything you're looking for although I havent spoke with him since the old facebook gunpage days.
So AR, I would recommend you calling Pelican State Armory in Abita and talk to Peter the owner. He will definetly get you going in the right direction. For everything else you mentioned A1 Gun and Repair in Metairie.