You may find sign and lettering vendors to be reluctant to remove vinyl lettering. This is because removing the lettering is a time-intensive job. There's really no way to rush it. Keep in mind that vinyl that has been left in place for a year or more may be hard to remove, especially if it's been exposed to much sun. It's more likely to crumble into small pieces that have to be carefully removed one at a time. It's also possible that the paint around the vinyl might be faded by sunlight while the paint underneath the vinyl has been protected and is thus still the original color--not unlike how carpeting underneath furniture that's been in place a long time can appear to be a different color, since the exposed carpeting has faded but the carpeting under the piece of furniture has not.
Use a heat gun to heat the decal surface.
Scrape vinyl away from the surface with a plastic removal squeegee.
Clean the surface with soap and water. Check to make sure there are no vinyl pieces left. If there is any vinyl left on the surface, heat it again with the heat gun and scrape it again with the plastic removal squeegee.
Make sure there is no adhesive remover left on the surface by wiping it down with alcohol. This is especially important if you plan to reapply vinyl lettering over the same area. If any adhesive remover is left, it will keep the new vinyl from sticking.
Scrape a razor blade along the glass at about a 30-degree angle. Your goal is to get the edge of the razor blade underneath the edge of the vinyl lettering and slowly peel it up.
Peel the vinyl lettering away from the window with your fingers if you can get a grip on it. Take care to keep your fingers as close to the window as possible when you peel. This will help keep the vinyl from breaking apart into small pieces that must be scraped off individually.
Continue using the razor blade to separate the vinyl letters from the window, then peeling with your fingers when possible, until they're completely removed.
Check the window for any signs of vinyl adhesive. If there is any adhesive still present, spray a vinyl adhesive remover on the window and wipe clean.
