Just because someone says, oh if the turtle dies it's okay, we'll replace him doesn't mean he's a reputable dealer. Actually I wouldn't trust many people that sell Alligator Snappers for $60 and make sure to tell their customers false information.
Anyways, he's a very beautiful turtle, I hope he pulls through! Just like with humans, a second opinion is necessary. The vet you went to may not have been a herp vet and said that he or she can't give shots because they don't know what they're doing.
EDIT: The breeding of pastels is questionable, I've heard that incubation temperatures are altered etc...Really there aren't many reputable online breeders or local breeders of Red Ear Sliders. I mean, they're so hardy and can "survive" in terrible conditions much better than other turtles.
