I Need to update photo edits to the images associated with my character.

I had to update the face on my character and want to simply swap the head image with new edits and keep the finished animation intact.
I also want to swap the body image. I made a new png and would like to update images associated with characters it. (NOT psd format if possible.)

I would be very happy if this is possible and as simple as the rest of the software.

Thanks!