I have just been through the process, on sm251, we only have the sender opening,  I sucked out all the fuel  through the filters with my vacume extraction,  opened up the outlet , put a light into the tank, I used a rag on a stick to wipe what I could, it was one of those job's that didn't really need to be done,  it was really clean, a small amount of dark colored somthing on the bottom. About the size of a saucer.