Re: No filter
Your system should have the capability of utilizing a filter, either at the return air grills within the house or inside the air handler. This is absolutely something that you can do yourself, all you need to know is what size filter to purchase. The best type of filter is the pleated type. You may also want to consider having your ducts cleaned. If your system has been without filters there will be significant dust build up within the system that will just be blown all over the house, regardless of installing a filter now.
I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!