also be prepared to hit it with a buffer and in extreme cases, wet sanding... it may a little newer/shinier underneath those decals. It's the only thing holding me back from doing mine right now.
Shadows under the decals was a concern of mine, too. Fortunately, my boat had no shadows where the stickers came off. The boat is stored outdoors each summer and it's a '99. I took off the decals last summer.