Well, Tankrookie first let me say I am so sorry for your loss. And I think you came to the right place to get your tank up and running again. Did your husband have any aquarium books? If not go to the library/bookstore and get a good beginner freshwater aquarium book. This will help you immensely and will be a good reference tool to go along with this site.
I personally recommend.
http://www.amazon.com/exec/obidos/A...9/sr=2-1/ref=pd_bbs_b_2_1/002-5528030-9101647
because it is a very easy to understand book.
Now first, from what I understand there are still fish in the aquarium? So we need to get the filter working. I'm not sure what type of filter you have, but you said it started making noise when you tried to change the filter (cartridge?) Is this a hang on the back of the aquarium style filter? If so it might have just made noise because the water emptied out of it. Try putting the cartridge in the filter and then filling the canister with water and then turning it on. It may make noise for a minute or so but the water should eventually start running through it. If not it may need to be taken apart and cleaned.
Also did your husband have any kind of testing kit to test the water? If not I would buy one if you can so you can test the water and see what kind of shape you are in. Mostly you want to test for ammonia/nitrite/and nitrates.
As far as cleaning the tank I would vacumn the gravel and do a partial water change. Did your husband use buckets to change the water or did he have a python? Either way is fine. You should do small water changes as much as you can. If you are very busy I would aim for 25-30% 1 every two weeks. You may need to do more than that in the beginning if your water tests are way off. The new water must be treated with water conditioner. You probably have some already if not you definitely need to buy some. This will take the chlorine and/or chlormines out of the tap water making it safe for your fish. Do you know what kind of fish you have left in the tank?
I wish I lived near you so I could come over and explain everything and show you what everything does, if you could find someone near you to this that would help you alot. But I believe if you get a book then you should be able to tell what different things your system has and how it was working before.
So for now I would work on the filter. If you can't get it working try taking it to the local fish store and see if they can tell if its broken or not. Once the filter works do a small water change and make sure you add water conditioner to the new water. The old fish water is great for gardens and houseplants. After the water change test the water and post the results here and we will know better what shape the tank is in.