This should be in the "How do I" section but start with having say 2 different sprits. Each sprite should have all the animation frames inside, not as a group but in the animation strip under the sprite editor.
When "SpritePowerup" overlaps "SpriteNormal"<
Create Spirte: PoweredUpSprite on layer "same as NormalSprite" at X=NormalSprite.X Y= NormalSprite.Y
Delete Object: NormalSprite
Then it is a matter of setting all the animations for any actions.