I hope you're still interested in extracting the geometry and textures from the monsters vs aliens game despite it's been months since you've asked this question.
I found a tool that let's you extract the meshes and textures from almost any 3d game. It's called ninjaripper. You have to run it as administrator and start the game using ninjaripper in order to make it work. Simply load up the game so you see ginormica and then hit F10. Ninjaripper will then save every geometry along with their textures that you're seeing in the game including characters and map geometries inside the ninjaripper folder at "C:/Users/<your windows account name>/Documents"
Here is the link where you can download it:https://gamebanana.com/tools/5638
I tested it on the monsters vs aliens game demo and was able to get the 3d models and textures from Ginormica, Missing Link, B.O.B, Insectorsaurus and the Alien Probe. I couldn't do the same on Dr. Cockroach because in the demo you can't play him. This may work if you have the full version of the game.
I've managed to import the 3d models of the characters into blender.
I hope that helps you. Best regards.