Nancy, a down sleeping bag can be soaked and hand washed in a large laundry sink or bathtub. Use mild laundry soap and let it soak overnight because it's oily. The next day, you can gently scrub the nylon with a soft brush if it's really dirty, but this may not be necessary.
Then drain and rinse at least twice. Now you can transfer it to your washing machine and spin it as dry as possible. You can dry it on low heat in a clothes drier, along with a clean pair of tennis shoes to fluff up the down. The whole process is a lot of work, but I have done it. The downside is, if the nylon is so old that it tears, you will have a mess of down to clean up.
I hope this helps.
Susan