i work at a sign shop so i deal with vinyl all day the best way to get it off would be to use a wallpaper steamer and a scraper of some sort idk where youd be able to find one but the ones we have at my work are called "lil chizlers". and if they were on there 10+ years theres no way youll be able to get them off in one piece its prob gonna be a lot of work. btw i wouldnt even try and use a razor to risky. and if you scrape it your gonna be left with a lot of glue to try and get off witch is a pain scrap as little as you have to and try and pull it off just use the scraper to get it started. hope that helps.

 

No scrapers, olive oil or aircraft stripper! You need a sticker remover wheel. Its basically a GIANT eraser. won't damage the paint when used at slow speeds. easy removal of any stickers without scratches. DO NOT USE OIL BASED PRODUCTS IF YOUR GOING TO BE PAINTING! Painter's nightmare! paint will not stick.