Enhance GIF Animation, Add Composited Characters

I have a seven second video capture stored in a GIF animation file. The video shows a cat driving a car. The GIF is obviously intended to be humorous. I need the existing video enhanced by replacing the cat driver with a different cat. I need an additional cat placed in the back seat. Eat cat will have a single line of dialog, showing as balloon text in the video. This project requires compositing skill, and because there is a non trivial geometry for substituting one cat image for another, it will require someone with significant experience doing this kind of work. Anyone who is good with motion graphics and video editing and who is familiar with tools and techniques to insert a 2D image into a region that then rotates and changes orientation and location within the field of view would be able to do this job. Could you point me to some samples of your work that illustrate this specific skill? The output of this job is a GIF animation, and it is extremely important that the total file size of the animation be under 2 MB. So you need to be extremely good with optimization issues like color density, adjusting numbers of frames to keep the animation file size tight, etc. I can point you to the animation file in private conversation, but I would like to see relevant portfolio work first. Please bid based a fixed price and inform me what is the range of possible costs.