QuiltersSon -- I am very sorry for the loss of your mom and brother. That is rough. Your mother's work is beautiful! When you start to organize the fabric piles try to keep projects together with their patterns if there are any left undone. Keep yardage separate from scraps. It is just easier to organize and keep track of things that way for selling. Rulers with rulers, thread with thread... you get the feeling right? You work with wood so keeping like materials together should be instinctive for you. As you box or bag things up, make sure you label it so you don't have to reopen it to remember what it is. That long arm is HUGE! I am sure someone may have mentioned contacting the manufacturer to find out if they have someone you should contact to resell it. I think Iceblossom's link to long arm University will get you the biggest bang for your buck but I don't know how quickly things sell on that site.
Some of the quilt stores in the area may be interested in purchasing some of her yardage or might even allow you to consign some items with them to sell. There is no fast or easy without an estate sale person taking care of it for you. Keep getting the word out. I hope you get some help soon. Thank you for sharing your mom's talent!!