In a 5-6 quart slow cooker, mix cream of mushroom soup with beef broth, onion soup mix and steak sauce. Whisk together well.
Then add in frozen meatballs. Cover and cook on low for 6-8 hours or on high 3-5 hours.
Just before meatballs are done, put a pot of water on the oven to boil for your egg noodles (make according to package directions.) Drain noodles well when done.
After meatballs have finished cooking, stir in sour cream.
Mix noodles and meatballs together or serve meatballs on top of noodles.
Creamy dishes aren't always great to freeze. They won't always heat up well and sometimes the gravy sort of separates when you go to reheat so I don't recommend freezing unless you perhaps have one of those machines with the special bags that sucks all the air out and then you can heat it up by boiling the bag in a pan (as long as the bag is boil-safe.) Otherwise, probably not wise to freeze.
You can store leftovers in the refrigerator (in an airtight lidded container) for up to 3 days. Just put it in a pot on the stove to reheat or in the microwave.