Thank you all for your comments, I'll pass them on to Rita!
Well I started with daily sesions of 10-15min on a perch, it took about 2 weeks for her to catch on her first trick, and it was easier from that moment because she already knew how it worked! They're really smart. Then I just ask her to do them from time to time so she won't forget them.
About the plucking yes, I'm sad to say she had plucked at the time. It was because my family and I had to go on a trip for a week, leaving her and my other birds at the care of a good friend, but I'm afraid she really REALLY missed us and was kind of depressed. During the time she was alone she would try to get out of the cage and pluck her feathers. It got really bad, didn't even want to eat.. When we got back she was really really exited thou, we took her to the vet and a blood test showed she had an infection, all this due to depression (according to what the vet said).
Oh I just remembered I have a video of the moment we came home, you could see her bare skin from all the feathers she plucked.. Anyway we took care of her, gave her vitamins and some medication and she was alright after. She's doing great now! All her feathers grew back and she's just heathy, happy and no more plucking! It's incredible how they bond with you..