I'm not entirely sure about Petco but with Petsmart, if you are hired you learn to take care of ALL of the animals the way the store wants *YOU* to take care of them. If the store is doing something wrong, you could make a suggestion but it doesn't mean that it can be changed because they have policies of their own they must follow. It's because of this training that there is no "true" specialists unless you really know your stuff!
Petstores should have a health guarantee, usually 7-14 days. You'd have to ask them. However, it would be cheaper going through a breeder, and if you find a reputable one, they too will have health guarantees. In order for them to take best effect, you need to take the bird in for a full workup, which includes fecal and a blood panel to ensure their health.
BirdBreeders.com - Bird Breeders Directory of Availability and Parrot Breeders
Also, be sure to find an avian vet near you!
http://www.birdboard.com/forum/get-h...-vet-here.html