You don't technically have to remove it. Just go into the Gummi directory, remove the Gummies from whatever ship you have them equipped on, and save. Use a cheating device to set the number of Gs in your inventory to one or zero, and then go back in and get the G from the chest. Setting values is basically the same as removing or adding. I wouldn't know which code to use, but I'm sure it's somewhere; most likely GameFAQs.