I'm removing an old(10year old decal ) and replacing it with a new one-same size and logo, I have heated and scraped the old one off with a plastic putty knife and a hair dryer and there remains a lay...
Yes, you have to get all the residue off for the new one to adhere. You might find that using a heat gun held about 8~10" away makes the sticker let go and take all the glue along with it. Or at least that's how it worked for me.