DON'T do it... even professionally done, it will end up cracking and looking worse then what you have now. I would look for a pro cleaner and take the seats into them. You'd be amazed at what they can get out of the seats. If it's the "pink" stains, those can be taken out as well... "stains are caused by a strain of bacterium known as Streptoverticillium reticulum that infests boat upholstery between the top layer of foam and underside of the vinyl"