Move existing animation of robot to new model and add textures

Hello!
I have a model of a quadrupped robot build in blender. It has skeleton and animation. I have updated an updated model of the robot build in step.

I need to translate existing animation to a new robot. (they are very similar)

Also I need to add textures to the robot. I have a sample render.

Everything has to be made in Blender. After you finish I'll need to export the model to Unity.

Inputs:
1. New step file
2. Old blender file with animation
3. Render of a previous robot.

Output:
1. Render of a new robot
2. Blender file with textures and animation
3. Help with importing animated robot to Unity

Please provide samples of your work, ask questions.

I'll give more information about the project when you accept NDA.