as to spraying plastic trim, be aware it'll probably crack and/or wear off really quickly unless you strip the outside layer of the plastic back then use proper plastic paint, which sets flexible. If you don't do that the paint won't adhere properly. Can't you just clean up the plastic, or replace it with less worn stuff from a breaker's?
Fitting new fabric is probably easier, all you really need to do is strip the old stuff off carefully and use that as templates to cut out your new material, but do renew any of the backing and support material, such as foam and ensure you get the right sort of material. It'll take a lot of patience and be prepared to make mistakes and have to go back over stuff, wasting material until you get the knack of it.
I have just removed, cleaned and replaced the cover of the back seat in our Citroen Pluriel, due to a wine stain. The word, "hog-ring" is now officially a swearword in our house. It looks OK but I didn't have to cut material, fit piping, refurb support material or anything and it still took me the best part of a day.
