Me and my wife "reupholstered" her car once. Was an older toyota and we semi-art-carred it, just a little.
Here's the process we used:
* get seats out of car an onto some tarps on the driveway, raised up for convenience if possible.
* clean and dust
* Get white tablecloths from thrift store (or any kind of slightly soft cloth)
* Using spray adhesive Scotch Super 77, cover with cloth. Use soft wood to help press into the creases. Use scissors and careful gluing and occasional hand-stitching to give it a decent fit.
* Now, get the cloth or covering you actually like... we used a whole bunch of crazy arab patterns we got at Mustaphas in Singapore for cheap. But whatever covering is your thing.
* The first layer was to make it nice and soft, and make a white foundation for your colors. Also, it was great practice on a layer that will be hidden.
* Apply second layer of cloth, also with Scotch 77.
Do whatever it takes, it's your car and your car seats and your cloth and it's gonna be fine. You can't break them. And it's 1000 times more awesome than duct tape. And 10000 times more awesome than boring old factory car seats.
:)
Edit: About the back seat, on her car, we managed to remove it. But you can do it in place, maybe using a less-aromatic adhesive...