Being in Wisconsin your chances of an outline are minimized compared to AZ or FL. You may need to polish the hood after you remove the stickers to remove any outline if it existsI want to remove my rubicon hood decals to replace with something else. Will there be a faint outline of it visible...about a year old? Or not really?
A hair dryer is fine. Absolutely no heat gun!!!!Never use a heat gun on your paint. Heat guns are used by painters to heat up and bubble paint so it can be scraped off. If warming it in the sun is not enough, a hair dryer is the furthest I would heat my paint.
This^^^If there is an outline it would buff out pretty easy. Paint correction is not hard, plenty of videos out there on how to do it correctly.