LOL my bad it was a really simple error, and some tweaking fixed it! I am just going to leave this up here in case someone else is trying to do the same thing! The correct code is:
-(void) callback
{
id fadeIn = [CCFadeTo actionWithDuration:0.5 opacity:0];
id fadeOut = [CCFadeTo actionWithDuration:0.5 opacity:255];
id change = [CCCallFunc actionWithTarget:self selector: @selector(changeText:)];
id sequence = [CCSequence actions: fadeIn, change, fadeOut, nil];
[_text runAction: sequence];
}