If its a whisper, you should be able to open it up and replace the carbon and keep your same bag on. Or one thing I do for filters like that when the bag gets ratty, is just float the new bag for a day or so before you change it and it works just fine. Plus you have bacteria all over every surface of your tank, so its no big deal. Unless your adding new fish or doing a major overhaul to your decorations or substrate at the same time, you shouldn't have any problems.
And welcome to AA