Hmm.. i cant tell you whether there is parrot behaviour classes in that respect, i can only give the advice i have used over the years.
Firstly, the change in attitude could be due to anything, without intruding too much into your personal affairs, have you recently moved home? Got a new partner? Or had a child or another pet in the house?
Birds are like children, they want and sometimes NEED all the attention, they dont like it when theres a new addition to the household which takes away their bond with you.
Secondly, assert your authority.. your the boss here
, try to make sure the cage is LOWER than you, the idea here is not to scare the bird but to show you are 'bigger' than them and thus the one in charge.
If you are scared of being bitten try some kevlar gloves (e.g. motorcycle gloves), but practice your grip on a soft toy first to ensure you can hold the bird firmly without hurting it (its not as easy as you think).
Another tip, and this is what they say to do with rodents, is to rub your hand in their bedding, obviously its not hygienic to do this with birds.. but covering your hands with something they dont like (e.g. chilli?) would mean they would avoid your hand/arm if you need to get stuff out of the cage.
Lastly, do not show fear to the bird, I once worked voluntarily at a rescue centre, which had housed a Sulphur-Crested Cockatoo (Not Umbrella) it used to say Hello to me all day, but when anyone tried to feed it or change water it would go for your hand... they used to distract it with a stick to grab the stuff out. The bird didnt have a name so i nicknamed it Pineapple/Piney.. (i dont know why
)
Needless to say i wouldn't settle for that and got a chunk taken out of the back of my hand for my effort, i wanted to scream, but i didnt... instead of screaming i was shouting a firm No at the bird, to my amazement it released, and then 'stepped up' onto my seemingly offered arm..
To say i was wary would be an understatement.. whether it was the fact somebody had finally bonded with that bird i could not say, but with my hand pumping blood i ushered the bird into the cage which it flew to and i closed.
Nobody seemed to believe me until a couple of weeks later, somebody had apparently not shut the birds cage door properly and it was divebombing anyone who came into the room... needless to say because of my previous heroics i was told to go 'sort it out', to the jeering of my 'co-workers'.
I was nervous i have to say, as i entered the room and the bird screeched a hello and then dived straight at me.. instantly i shut my eyes, expected to be ripped apart by claws and the beak.. instead i felt a flutter near my face and the claws dig into my shoulder... Yes, the vicious cockatoo nobody could go near had landed on my shoulder.. and then to everyones amazement (my co-workers were all fighting to look through the window on the door) the bird started preening itself right there and then..
After extending my arm back to its cage it crawled down and went back in, no problem... i made sure it was closed and that was that... nobody could believe it.. they called me The Bird Whisperer every day after that...