In addition to all those suggestions, the best thing I've found
for introducing new foods and getting them accepted is to eat
with the bird. They are very flock oriented and eating is a
flock activity. Fix both of you a plate and sit down and eat
with the bird. Be sure to make all kinds of "yummy yummmy", etc.
sounds to show how much you are enjoying yours. It will take
some time but I've never seen one who can resist trying something
for very long if they see you enjoying it. I'd also urge a check
up with a good avian vet if that's the kind of diet the bird has
been on for a long time.