An Avian Vet is always preferred, but if none are available a vet who is a certified ZOO vet ("CertZooMed" means they've done extra work with exotics) is more often than not experienced with 'exotics and avian' and would be better than your standard vet.
I do think you're worrying over nothing at the moment though. Birds preen, feathers fall, sometimes they'll look at you with a huge feather in their mouth "Mummy, look what I just pulled!". It'll just be feathers that needed a little nudge to come out anyway during the moult.
Can tell you're a new parront, worryworryworry! If they sneeze, they're dying?! Sometimes it just is what it is, a sneeze, a loose feather, an itch that needed to be scratched, etc.
He'll be fine
