I'd park the vehicle so the sun is on it long enough to be pretty HOT to the touch. Given that its winter, you have to go past this step and start with the hair dryer which you will use several times as you go...then WD-40.....then try to lift an edge and try to peel it off. If you get it to start to lift, the hair dryer and more WD-40 may do the trick. I like the plastic scraper, or a credit card I guess as a metal tool will probably scratch the paint.
In the end if the paint has faded because the sticker has "protected it" for years and if it shadows the paint job, you might just have to live with it or find another sticker more to your liking to cover it up!
Goo Gone is a good product and I love Dawn to remove any petroleum products from wooden hammer shafts to greasy parts. They use it to get bunker fuel off birds when a ship sinks or a pipeline bursts and it works.