If your plastic panels are in good shape, painting them is certainly more economical, but it's your budget and you can do whatever you want. If you decide to paint, be sure to clean them really well first. The SEM paint I used was water based and I needed to pre coat with anther SEM product called Sand Free. Both put into aerosol cans. It required that the paint be applied (sprayed) when the Sand Free was still wet so it would adhere properly. The vinyl paint was just a spray on I think. You can get replacement vinyls from MSA in red to match the upholstery kit if you don't want to paint that part. I don't have any experience with the door panels you mentioned from Z car depot, but unless you want black, you'll need to paint them red also.