Hi Zippi,
Glad that you found "what is going on".
To remove the glued in servos and depending on how many faces have been glued I think all you can do is cut the foam all around . On the sides itshould not be too difficult. Leave the glue on the servos till they are out and clean that when the servos are in your hands.
If they are glued on the back side you may have to cut in from behind and then make pieces of foam to fill in the cavity from behind by gluing in some foam blocks well fitted in.
Suggest you do not glue the replacements in.
There is many ways I can think of to fasten the new ones in place. I will leave that to your initiative. I know what I would do but I am trying to avoid negative comments.
I cannot think of a better way to remove them.
When there is a will there is a way __
__ .
Good luck and enjoy your work.
Zor